U.S. patent application number 11/584167 was filed with the patent office on 2007-05-31 for photonic crystal fibers and medical systems including photonic crystal fibers.
This patent application is currently assigned to OmniGuide, Inc., a Massachusetts corporation. Invention is credited to Charalambos Anastassiou, Gregor Dellemann, Yoel Fink, Steven A. Jacobs, Uri Kolodny, Robert Payne, Gil Shapira, Max Shurgalin, Burak Temelkuran, David Torres, Tairan Wang, Ori Weisberg.
Application Number | 20070122096 11/584167 |
Document ID | / |
Family ID | 35375245 |
Filed Date | 2007-05-31 |
United States Patent
Application |
20070122096 |
Kind Code |
A1 |
Temelkuran; Burak ; et
al. |
May 31, 2007 |
Photonic crystal fibers and medical systems including photonic
crystal fibers
Abstract
In general, in one aspect, the invention features methods that
include directing radiation to a target location of a patient
through a photonic crystal fiber, the photonic crystal fiber having
a hollow core and flowing a fluid through the hollow core to the
target location of the patient.
Inventors: |
Temelkuran; Burak; (Boston,
MA) ; Anastassiou; Charalambos; (Malden, MA) ;
Torres; David; (Stoughton, MA) ; Shapira; Gil;
(Brookline, MA) ; Shurgalin; Max; (Lexington,
MA) ; Dellemann; Gregor; (Ulm, DE) ; Weisberg;
Ori; (Kfar mordechai, IL) ; Jacobs; Steven A.;
(Needham, MA) ; Wang; Tairan; (Chelmsford, MA)
; Kolodny; Uri; (Sede Warburg, IL) ; Payne;
Robert; (Wellesley, MA) ; Fink; Yoel;
(Brookline, MA) |
Correspondence
Address: |
FISH & RICHARDSON PC
P.O. BOX 1022
MINNEAPOLIS
MN
55440-1022
US
|
Assignee: |
OmniGuide, Inc., a Massachusetts
corporation
|
Family ID: |
35375245 |
Appl. No.: |
11/584167 |
Filed: |
October 20, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11102299 |
Apr 8, 2005 |
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11584167 |
Oct 20, 2006 |
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60560458 |
Apr 8, 2004 |
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60561020 |
Apr 9, 2004 |
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60584098 |
Jun 30, 2004 |
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60628462 |
Nov 16, 2004 |
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60640536 |
Dec 30, 2004 |
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60658531 |
Mar 4, 2005 |
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Current U.S.
Class: |
385/126 |
Current CPC
Class: |
G02B 6/02304 20130101;
A61B 18/24 20130101; A61B 2018/00017 20130101; A61B 18/22 20130101;
A61B 2018/2288 20130101; G02B 6/032 20130101; G02B 6/02385
20130101; G02B 6/42 20130101; A61B 18/201 20130101 |
Class at
Publication: |
385/126 |
International
Class: |
G02B 6/02 20060101
G02B006/02; G02B 6/036 20060101 G02B006/036 |
Claims
1-31. (canceled)
32. A system, comprising: a waveguide including a hollow core
extending along a waveguide axis, the waveguide being configured so
that during operation the waveguide guides radiation along the
waveguide axis from an input end to an output end of the waveguide
and delivers the radiation to a target location; a fluid source
configured so that during operation of the system the fluid source
delivers fluid to the hollow core of the waveguide via the input
end of the waveguide; and a tube extending along the waveguide
axis, the tube being configured so that during operation of the
system the tube channels fluid exiting the output end of the
waveguide away from the output end and away from the target
location.
33. The system of claim 32, wherein the waveguide is a photonic
crystal fiber.
34. The system of claim 33, wherein the photonic crystal fiber
comprises an all-dielectric confinement region configured to guide
the radiation along the waveguide axis by substantially confining
the radiation to the hollow core.
35. The system of claim 32, further comprising a jacket surrounding
a portion of waveguide and a portion of tube.
36. The system of claim 35, wherein waveguide, tube, and jacket
form a flexible duct.
37. The system of claim 35, further comprising a cap positioned to
cover the output end of waveguide.
38. The system of claim 37, wherein during operation of the system
the cap prevents the fluid exiting the output end of the waveguide
from reaching the target location.
39. The system of claim 37, wherein the cap comprises a window
positioned to transmit radiation exiting the output end of the
waveguide during operation of the system.
40. The system of claim 37, wherein the cap comprises an exhaust
port that during operation of the system provides a pathway for the
fluid exiting the core to flow into the tube.
41. The system of claim 32, further comprising a laser configured
to direct radiation into the input end of the waveguide during
operation of the system.
42. The system of claim 41, wherein the laser is a CO.sub.2
laser.
43. The system of claim 32, wherein the fluid is a gas.
44. The system of claim 32, further comprising a coupling assembly
configured to deliver radiation from a radiation source and fluid
from the fluid source to the hollow core of waveguide during
operation of the system.
45. The system of claim 32, further comprising a pump configured to
draw fluid through the tube away from the output end of the
waveguide during operation of the system.
46. The system of claim 32, further comprising a handpiece attached
to the waveguide, the handpiece being configured to allow an
operator to control the orientation of the output end to direct the
radiation to the target location during operation of the
system.
47. A method, comprising: simultaneously guiding radiation and
fluid through a waveguide having a hollow core; directing the
guided radiation exiting the waveguide towards a target location;
and directing the fluid exiting the waveguide away from the target
location of the patient.
48. The method of claim 47, wherein the fluid exiting the waveguide
is directed away from the target location by directing the fluid
through a tube, where the tube and the waveguide extend along a
common axis.
49. The method of claim 48, wherein the fluid exiting the waveguide
is prevented from reaching the target location by a cap at the
output end of the waveguide that directs the fluid from the
waveguide to the tube.
50. The method of claim 49, wherein the cap comprises a window that
transmits radiation exiting the waveguide to the target
location.
51. The method of claim 47, wherein the fluid is a gas.
52. The method of claim 47, wherein the fluid reduces heating of
the waveguide by the radiation.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] Under 35 USC .sctn.119(e)(1), this application claims the
benefit of Provisional Patent Application 60/560,458, entitled
"PHOTONIC CRYSTAL FIBER APPLICATIONS," filed on Apr. 8, 2004,
Provisional Patent Application 60/561,020, entitled "PHOTONIC
CRYSTAL FIBER APPLICATIONS," filed on Apr. 9, 2004, Provisional
Patent Application 60/584,098, entitled "PHOTONIC CRYSTAL FIBER
APPLICATIONS," filed on Jun. 30, 2004, Provisional Patent
Application 60/628,462, entitled "PHOTONIC CRYSTAL FIBER
APPLICATIONS," filed on Nov. 16, 2004, Provisional Patent
Application 60/640,536, entitled "OMNIGUIDE PHOTONIC BANDGAP FIBERS
FOR FLEXIBLE DELIVERY OF CO.sub.2 LASERS IN LARYNGOLOGY," filed on
Dec. 30, 2004, and Provisional Patent Application 60/658,531,
entitled "PHOTONIC CRYSTAL FIBERS," filed on Mar. 4, 2005. The
contents of all the above-listed provisional patent applications
are hereby incorporated by reference in their entirety.
BACKGROUND
[0002] Lasers are prevalent in many areas of medicine today. For
example, lasers find application in diverse medical areas, such as
surgery, veterinary medicine, dentistry, ophthalmology, and in
aesthetic medical procedures.
[0003] In many of these applications, an optical fiber is used to
deliver radiation from a laser to the target region of the patient.
Conventional optical fibers are excellent waveguides for radiation
having wavelengths in the visible or near-infrared portion of the
electromagnetic spectrum (e.g., wavelengths of about 2 microns or
less). However, conventional optical fibers are, in general, not
suitable in applications where high power laser radiation with
relatively long wavelengths is used. Accordingly, many medical
laser systems that deliver high power (e.g., about I0 Watts or
more), long wavelength (e.g., greater than about 2 microns), do so
using an articulated arm that includes optical components that
guide the laser radiation through rigid conduits or free space from
the laser to the target.
SUMMARY
[0004] Photonic crystal fibers can be used in medical laser systems
to guide radiation from a radiation source (e.g., a laser) to a
target location of a patient. In general, photonic crystal fibers
include a region surrounding a core that provides extremely
effective confinement of certain radiation wavelengths to the core.
These so-called confinement regions can be formed exclusively from
amorphous dielectric materials (e.g., glasses and/or polymers), and
can provide effective confinement while still being relatively
thin. Accordingly, photonic crystal fibers can include thin,
flexible fiber's capable of guiding extremely high power
radiation.
[0005] Moreover, photonic crystal fibers can be drawn from a
preform, resulting in fibers that are relatively inexpensive to
produce compared to other waveguides that are not drawn. Fiber
manufacturing techniques also provides substantial production
capacity, e.g., thousands of meters of fiber can be drawn from a
single preform. The conversion in the draw process from a
relatively short preform to very long lengths of fiber can
effectively smooth out any perturbations from the desired structure
that exist in the preform, producing low-loss, low-defect
fiber.
[0006] In general, in a first aspect, the invention features
systems, including a photonic crystal fiber including a core
extending along a waveguide axis and a dielectric confinement
region surrounding the core, the dielectric confinement region
being configured to guide radiation along the waveguide axis from
an input end to an output end of the photonic crystal fiber. The
systems also includes a handpiece attached to the photonic crystal
fiber, wherein the handpiece allows an operator to control the
orientation of the output end to direct the radiation to a target
location of a patient.
[0007] Embodiments of the systems can include one or more of the
following features and/or aspects of other aspects.
[0008] The handpiece can include an endoscope. The endoscope can
include a flexible conduit and a portion of the photonic crystal
fiber is threaded through a channel in the flexible conduit. The
endoscope can include an actuator mechanically coupled to the
flexible conduit configured to bend a portion of the flexible
conduit thereby allowing the operator to vary the orientation of
the output end. The actuator can be configured to bend the portion
of the flexible conduit so that the bent portion of the flexible
conduit has a radius of curvature of about 12 centimeters or less
(e.g., about 10 centimeters or less, about 8 centimeters or less,
about 5 centimeters or less, about 3 centimeters or less). The
actuator can be configured to bend the flexible conduit within a
bend plane. The handpiece can be attached to the photonic crystal
fiber to maintain an orientation of the dielectric confinement
region to control the orientation of the photonic crystal fiber
about its waveguide axis within the flexible conduit. The
attachment between the handpiece and the photonic crystal fiber can
prevent twisting of the fiber by more than about 10 degrees (e.g.,
by more than about 5 degrees) while maintaining operation. The
endoscope can further include an auxiliary conduit including a
first portion coupled to the flexible conduit, wherein the photonic
crystal fiber is threaded through a channel in the auxiliary
conduit into the channel of the flexible conduit, the auxiliary
conduit further comprising a second portion moveable with respect
to the first portion, wherein the photonic crystal fiber is
attached to the second portion and moving the second portion allows
the operator to extend or retract the output end relative to an end
of the flexible conduit. The second portion can extend or retract
with respect to the first portion. The auxiliary conduit can be a
rigid conduit.
[0009] In some embodiments, the handpiece includes a conduit and a
portion of the photonic crystal fiber is threaded through the
conduit. The conduit can include a bent portion. The conduit can be
formed from a deformable material. The handpiece can further
include an actuator mechanically coupled to the conduit configured
to bend a portion of the conduit thereby allowing the operator to
vary the orientation of the output end.
[0010] The handpiece can include a tip extending past the output
end that provides a minimum standoff distance of about I millimeter
or more between the output end and the target location.
[0011] The photonic crystal fiber can be sufficiently flexible to
guide the radiation to the target location while a portion of the
photonic crystal fiber is bent through an angle of about 90 degrees
or more and the portion has a radius of curvature of about 12
centimeters or less. The radiation can have an average power at the
output end of about 1 Watt or more while the portion of the
photonic crystal fiber is bent through an angle of about 90 degrees
or more and the portion has a radius of curvature of about 12
centimeters or less. The radiation can have an average power at the
output end of about 5 Watts or more while the portion of the
photonic crystal fiber is bent through an angle of about 90 degrees
or more and the portion has a radius of curvature of about 12
centimeters or less. The photonic crystal fiber can be sufficiently
flexible to guide the radiation to the target location while the
portion of the photonic crystal fiber is bent through an angle of
about 90 degrees or more and the portion has a radius of curvature
of about 10 centimeters or less (e.g., about 5 centimeters or
less).
[0012] The dielectric confinement region can include a layer of a
first dielectric material arranged in a spiral around the waveguide
axis. The dielectric confinement region can further include a layer
of a second dielectric material arranged in a spiral around the
waveguide axis, the second dielectric material having a different
refractive index from the first dielectric material. The first
dielectric material can be a glass (e.g., a chalcogenide glass).
The second dielectric material can be a polymer. The dielectric
confinement region can include at least one layer of a chalcogenide
glass. The dielectric confinement region can include at least one
layer of a polymeric material. In some embodiments, the dielectric
confinement region includes at least one layer of a first
dielectric material extending along the waveguide axis and at least
one layer of a second dielectric material extending along the
waveguide axis, wherein the first and second dielectric materials
can be co-drawn with the first dielectric material.
[0013] The core can be a hollow core. The system can further
include a fluid source coupled to the input end or output end,
wherein during operation the fluid source supplies a fluid through
the core. The fluid can be a gas.
[0014] The core can have a diameter of about 1,000 microns or less
(e.g., about 500 microns or less). The photonic crystal fiber can
have an outer diameter of about 2,000 microns or less at the output
end.
[0015] In some embodiments, the system further includes an optical
waveguide and a connector that attaches the optical waveguide to
the photonic crystal fiber. The optical waveguide can be a second
photonic crystal fiber. The system can also include a conduit
surrounding the optical waveguide. The conduit can be more rigid
than the optical waveguide. The system can include a fluid source
coupled to the conduit and wherein during operation the fluid
source supplies a fluid to the conduit.
[0016] The system can further include a laser to produce the
radiation and direct it towards the input end of the photonic
crystal fiber. The laser can be a CO.sub.2 laser. The radiation can
have a wavelength of about 2 microns or more. In some embodiments,
the radiation has a wavelength of about 10.6 microns.
[0017] In certain embodiments, the system further includes an
auxiliary radiation source and at least one additional fiber
mechanically coupled to the photonic crystal fiber, the additional
waveguide being configured to deliver auxiliary radiation from the
auxiliary radiation source to the target location. The additional
fiber can be mechanically coupled to the photonic crystal fiber by
the handpiece. The auxiliary radiation source can be a second
laser, different from the laser positioned to direct the radiation
to the input end of the photonic crystal fiber. The second laser
can be an Nd:YAG laser, a diode laser, or a pulsed dye laser. The
auxiliary radiation can have a wavelength in the visible portion of
the electromagnetic spectrum.
[0018] At least a portion of the photonic crystal can be
sterilized.
[0019] In general, in another aspect, the invention features
articles that include a length of a photonic crystal fiber, the
photonic crystal fiber including a core extending along a waveguide
axis and a dielectric confinement region surrounding the core, the
dielectric confinement region being configured to guide radiation
along the waveguide axis from an input end to an output end of the
photonic crystal fiber, wherein the length of the photonic crystal
fiber is sterilized.
[0020] The articles can further include a sealed package containing
the length of the photonic crystal fiber. Embodiments of the
articles can include one or more of the features of other
aspects.
[0021] In general, in a further aspect, the invention features
methods that include directing radiation into an input end of a
photonic crystal fiber and using a handpiece attached to the
photonic crystal fiber to control the orientation of an output end
of the photonic crystal fiber and direct radiation emitted from the
output end towards a target location of a patient. Embodiments of
the methods can include one or more of the features of other
aspects.
[0022] In general, in another aspect, the invention features
methods that include directing radiation to a target location of a
patient through a photonic crystal fiber, the photonic crystal
fiber having a hollow core and flowing a fluid through the hollow
core to the target location of the patient.
[0023] Embodiments of the methods can include one or more of the
following features and/or features of other aspects.
[0024] The radiation can have sufficient power to incise, excise,
or ablate tissue at the target location. The fluid can have a
sufficient pressure and temperature to coagulate blood at the
target location.
[0025] The methods can include bending the photonic crystal fiber
while directing the radiation and the fluid to the target location.
Bending the fiber can include bending a portion of the fiber
through about 45.degree. or more to have a radius of curvature of
about 12 centimeters or less.
[0026] Directing the radiation and the fluid to the target location
can include holding a portion of a handpiece attached to the
photonic crystal fiber and controlling the orientation of the
output end using the handpiece.
[0027] The fluid can be a gas, a liquid, or a superfluid. In
embodiments where the fluid is gas, the gas can have a pressure of
about 0.5 PSI or more (e.g., about 1 PSI or more) at the output
end. The gas can have a temperature of about 50.degree. C. or more
(e.g., about 80.degree. C. or more) at the target location. The gas
can be air. The gas can include carbon dioxide, oxygen, nitrogen,
helium, neon, argon, krypton, or xenon. The gas can be a
substantially pure gas. For example, the gas can include about 98%
or more of a single component gas. Alternatively, in some
embodiments, the gas is gas mixture.
[0028] The fluid can be flowed into the hollow core at a rate of
about 1 liter per minute or more (e.g., about 2 liters per minute
or more, about 5 liters per minute or more, about 8 liters per
minute or more).
[0029] The radiation can have a wavelength of about 2 microns or
more (e.g., about 10.6 microns). The radiation can have an average
power of about 1 Watt or more at the target location.
[0030] In general, in a further aspect, the invention features
apparatus that include a photonic crystal fiber including a core
extending along a waveguide axis and a dielectric confinement
region surrounding the core, the dielectric confinement region
being configured to guide radiation along the waveguide axis from
an input end to an output end of the photonic crystal fiber, and a
sleeve coupled to the output end of the photonic crystal fiber to
allow the radiation to pass through the sleeve and exit the sleeve
through a primary opening, the sleeve further comprising one or
more secondary openings positioned so that gas flowed into the
sleeve exits the sleeve through the secondary openings.
[0031] Embodiments of the apparatus can include one or more of the
following features and/or features of other aspects.
[0032] The gas flowed into the sleeve can exit the sleeve through
the primary opening in addition to through the secondary openings.
The apparatus can further include a transparent element positioned
between the primary opening and the secondary openings that
substantially transmits the radiation as it passes through the
sleeve. The transparent element can substantially prevent gas from
exiting the sleeve through the primary opening. The transparent
element can include ZnSe.
[0033] The apparatus can further include a conduit positioned
relative to the secondary opening so that gas exiting the sleeve
through the secondary opening is drawn into an input end of the
conduit.
[0034] The secondary opening can be positioned near to the primary
opening. The primary opening can have a diameter that is smaller
than an outer diameter of the photonic crystal fiber at the output
end. The apparatus can further include a focusing element attached
to the sleeve to focus the radiation passing through the sleeve.
Alternatively, or additionally, the can include a reflecting
element attached to the sleeve to reflect the radiation passing
through the sleeve.
[0035] In general, in another aspect, the invention features
apparatus that include an assembly including a radiation input port
configured to receive radiation from a radiation source and an
output port configured to couple the radiation to a photonic
crystal fiber, the assembly further including a retardation element
positioned to modify a polarization state of the radiation received
from the radiation source before it is coupled to the photonic
crystal fiber.
[0036] Embodiments of the apparatus can include one or more of the
following features and/or features of other aspects.
[0037] The assembly can further include a gas input port configured
to receive gas from a gas source. The photonic crystal fiber can
have a hollow core. The output port can be further configured to
couple the gas received from the gas source into the hollow core of
the photonic crystal fiber. The apparatus can include the gas
source.
[0038] The retardation element can be a reflective retardation
element. The apparatus can include the radiation source, wherein
the radiation from the radiation source includes radiation having a
wavelength .lamda.. The reflective retardation element can include
a mirror and a retardation layer having an optical thickness of
about .lamda. or less disposed on a surface of the mirror. The
retardation layer can have an optical thickness of about .lamda./4
along a direction about 45.degree. relative to a normal to the
surface of the mirror. .lamda. can be about 2 microns or more. For
example, .lamda. can be about 10.6 microns.
[0039] The retardation element can be a transmissive retardation
element.
[0040] The retardation element can modify the polarization state of
the radiation from a substantially linear polarization state to a
substantially non-linear polarization state. The substantially
non-linear polarization state can be a substantially circular
polarization state.
[0041] The assembly can further include a focusing element
configured to focus the radiation entering the assembly at the
radiation input port to a waist near the output port. The focusing
element can focus the radiation to a waist diameter of about 1,000
microns or less (e.g., about 500 microns or less). The focusing
element can be a lens. The lens can include ZnSe.
[0042] The apparatus can further include the photonic crystal
fiber.
[0043] In general, in another aspect, the invention features
methods that include modifying a polarization state of radiation
emitted from a laser, directing the radiation having the modified
polarization state into an input end of a photonic crystal fiber
having a hollow core, and coupling gas from a gas source into the
input end of the hollow core.
[0044] Embodiments of the methods can include one or more of the
features or other aspects.
[0045] In general, in another aspect, the invention features
methods that include guiding radiation through an optical waveguide
to tissue of a patient, wherein the optical waveguide has a hollow
core, and directing gas to the tissue while guiding the radiation,
wherein the radiation and gas are sufficient to cut (e.g., excise
or ablate) the tissue and to substantially coagulate exposed
blood.
[0046] In general, in a further aspect, the invention features a
medical laser system, including a laser, an optical waveguide
having a hollow core, a delivery device, a gas source (e.g., a
cylinder of gas, a compressor, a blower) configured to deliver a
gas to the tissue, wherein during operation radiation from the
laser and gas from the gas source are delivered to tissue of a
patient, wherein the radiation and gas are sufficient to incise the
tissue and substantially coagulate exposed blood.
[0047] In general, in another aspect, the invention features a
system, including a laser having an output terminal, a photonic
crystal fiber having an input end and an output end, the input end
being configured to accept radiation emitted from the output
terminal, and a delivery device for allowing an operator to direct
radiation emitted from the output end to target tissue.
[0048] In general, in another aspect, the invention features a
system, including a CO.sub.2 laser, an endoscope, and a photonic
crystal fiber, wherein during operation the photonic crystal fiber
guides radiation from the CO.sub.2 laser through the endoscope to
target tissue.
[0049] In general, in a further aspect, the invention features a
coupler for coupling gas and radiation into one end of a hollow
core of a fiber.
[0050] Embodiments of the invention may include one or more of the
following features.
[0051] The gas can be directed through the hollow core of the
optical waveguide or the gas can be directed to the tissue through
a tube separate from the hollow core. The radiation can be
delivered from a laser (e.g., a CO.sub.2 laser). The laser can have
an output power of about 5 Watts or more (e.g., about 10 Watts or
more, about 15 Watts or more, about 20 Watts or more, about 50
Watts or more, about 100 Watts or more). The radiation delivered to
the tissue can have a power of about 1 Watt or more as measured at
the distal end of the optical waveguide (e.g., about 2 Watts or
more, 5 Watts or more, 8 Watts or more, 10 Watts or more, about 20
Watts or more, about 50 Watts or more). The radiation can have a
wavelength of about 10.6 microns. The gas can have a flow rate of
about 1 liter/min or more (e.g., about 2 liter/min or more, about 5
liter/min or more, about 8 liter/min or more, about 10 liter/min or
more, about 12 liter/min or more, about 15 liter/min or more, about
20 liter/min or more).
[0052] The pressure of the gas exiting the hollow core can be
relatively high. For example, the gas pressure exiting the fiber
can correspond to a flow rate of about 1 liter/min or more (e.g.,
about 2 liter/min or more, about 5 liter/min or more, about 8
liter/min or more, about 10 liter/min or more, about 12 liter/min
or more, about 15 liter/min or more, about 20 liter/min or more)
through a 1 meter length of fiber having a core diameter of about
500 .mu.m.
[0053] The gas can include air, nitrogen, oxygen, carbon dioxide or
a noble gas (e.g., He, Ne, Ar, Kr, and/or Xe). The gas can include
substantially only one compound (e.g., about 98% or more of one
compound, about 99% or more, about 99.5% or more, about 99.8% or
more, about 99.9% or more). Alternatively, in some embodiments, the
gas can include a mixture of different compounds (e.g., air).
[0054] The method can further include excising tissue with the
radiation. The optical waveguide can be a photonic crystal fiber
(e.g., a Bragg fiber). The gas can have a temperature of about
50.degree. C. or more at the tissue (e.g., about 60.degree. C. or
more, about 70.degree. C. or more, about 80.degree. C. or more,
about 90.degree. C. or more, about 100.degree. C. or more). The
method can further include bending the fiber while delivering
radiation to the tissue. The fiber bend can have a radius of
curvature of about 12 cm or less (e.g., about 10 cm or less, about
8 cm or less, about 7 cm or less, about 6 cm or less, about 5 cm or
less, about 4 cm or less, about 3 cm or less, about 2 cm or
less).
[0055] A number of references are incorporated herein by reference.
In case of conflict, the present application will control.
[0056] The details of one or more embodiments of the invention are
set forth in the accompanying drawings and the description below.
Other features and advantages of the invention will be apparent
from the description and drawings, and from the claims.
DESCRIPTION OF DRAWINGS
[0057] FIG. 1 is a schematic diagram of an embodiment of a laser
medical system that includes a photonic crystal fiber.
[0058] FIG. 2A is a cross-section view of an embodiment of a
photonic crystal fiber.
[0059] FIG. 2B-2D are cross-sectional views of embodiments of
confinement regions for photonic crystal fibers.
[0060] FIG. 3 is a cross-sectional view of a photonic crystal fiber
including a cladding having an asymmetric cross-section.
[0061] FIG. 4A-4D are cross-sectional views of embodiments of
sleeves attached to an output end of a photonic crystal fiber.
[0062] FIG. 5A and 5B are diagrams of embodiments of coupling
assemblies for coupling radiation and a fluid into a hollow core of
a photonic crystal fiber.
[0063] FIG. 6 is a diagram of a handpiece that includes a malleable
conduit.
[0064] FIG. 7A is a schematic diagram of another embodiment of a
laser medical system including a photonic crystal fiber.
[0065] FIG. 7B is a diagram of an endoscope.
[0066] FIG. 7C is a schematic diagram of a further embodiment of a
medical laser system including a photonic crystal fiber.
[0067] FIG. 8 is a schematic diagram of a portion of a medical
laser system that includes a photonic crystal fiber and a second
fiber waveguide.
[0068] FIG. 9 is a schematic diagram of a portion of a medical
laser system that includes a photonic crystal fiber and a tube for
exhausting fluid from the fiber.
[0069] Like reference symbols in the various drawings indicate like
elements.
DETAILED DESCRIPTION
[0070] Referring to FIG. 1, a medical laser system 100 includes a
CO.sub.2 laser 110, and a photonic crystal fiber 120 having a
hollow core to guide radiation 112 from the laser to a target
location 99 of a patient. Radiation 112 has a wavelength of 10.6
microns. Laser radiation 112 is coupled by a coupling assembly 130
into the hollow core of photonic crystal fiber 120, which delivers
the radiation through a handpiece 140 to target location 99. During
use, an operator (e.g., a medical practitioner, such as a surgeon,
a dentist, an ophthalmologist, or a veterinarian) grips a portion
142 of handpiece 140, and manipulates the handpiece to direct laser
radiation 113 emitted from an output end of photonic crystal fiber
120 to target location 99 in order to perform a therapeutic
function at the target location. For example, the radiation can be
used to excise, incise, ablate, or vaporize tissue at the target
location.
[0071] CO.sub.2 laser 110 is controlled by an electronic controller
150 for setting and displaying operating parameters of the system.
The operator controls delivery of the laser radiation using a
remote control 152, such as a foot pedal. In some embodiments, the
remote control is a component of handpiece 140, allowing the
operator to control the direction of emitted laser radiation and
delivery of the laser radiation with one hand or both hands.
[0072] In addition to grip portion 142, handpiece 140 includes a
stand off tip 144, which maintains a desired distance (e.g., from
about 0.1 millimeters to about 30 millimeters) between the output
end of fiber 120 and target tissue 99. The stand off tip assist the
operator in positioning the output end of photonic crystal fiber
120 from target location 99, and can also reduce clogging of the
output end due to debris at the target location. In some
embodiments, handpiece 140 includes optical components (e.g., a
lens or lenses), which focus the beam emitted from the fiber to a
desired spot size. The waist of the focused beam can be located at
or near the distal end of the stand off tip.
[0073] In some embodiments, fiber 120 can be easily installed and
removed from coupling assembly 130, and from handpiece 140 (e.g.,
using conventional fiber optic connectors). This can facilitate
ease of use of the system in single-use applications, where the
fiber is replaced after each procedure.
[0074] Typically, CO.sub.2 laser 110 has an average output power of
about 5 Watts to about 80 Watts at 10.6 microns (e.g., about 10
Watts or more, about 20 Watts or more). In many applications, laser
powers of about 5 Watts to about 30 Watts are sufficient for the
system to perform its intended function. For example, where system
100 is being used to excise or incise tissue, the radiation is
confined to a small spot size and a laser having an average output
power in this range is sufficient.
[0075] In certain embodiments, however, laser 110 can have an
output power as high as about 100 Watts or more (e.g., up to about
500 Watts). For example, in applications where system 100 is used
to vaporize tissue over a relatively large area (e.g., several
square millimeters or centimeters), extremely high power lasers may
be desirable.
[0076] Photonic crystal fiber can deliver the radiation from laser
110 to the target location with relatively high efficiency. For
example, the fiber average output power can be about 50% or more of
the fiber input energy (e.g., about 60% or more, about 70% or more,
about 80% or more). Accordingly, the fiber's output power can be
about 3 Watts or more (e.g., about 8 Watts or more, about 10 Watts
or more, about 15 Watts or more).
[0077] In certain embodiments, however, the average output power
from the fiber can be less than 50% of the laser power, and still
be sufficiently high to perform the intended procedure. For
example, in some embodiments, the fiber average output power can be
from about 20% to about 50% of the laser average output power.
[0078] The length of photonic crystal fiber 120 can vary as
desired. In some embodiments, the fiber is about 1.2 meters long or
more (e.g., about 1.5 meters or more, about 2 meters or more, about
3 meters or more, about 5 meters or more). The length is typically
dependent on the specific application for which the laser system is
used. In applications where laser 110 can be positioned close to
the patient, and/or where the range of motion of the handpiece
desired for the application is relatively small, the length of the
fiber can be relatively short (e.g., about 1.5 meters or less,
about 1.2 meters or less, about 1 meter or less). In certain
applications, the length of fiber 120 can be very short (e.g.,
about 50 centimeters or less, about 20 centimeters or less, about
10 centimeters or less). For example, very short lengths of
photonic crystal fiber may be useful in procedures where the system
can deliver radiation from the laser to the fiber by some other
means (e.g., a different waveguide or an articulated arm). Very
short fiber lengths may be useful for nose and ear procedures, for
example.
[0079] However, in applications where it is inconvenient for the
laser to be placed in close proximity to the patient and/or where a
large range of motion of the handpiece is desired, the length of
the fiber is longer (e.g., about 2 meters or more, about 5 meters
or more, about 8 meters or more). For example, in surgical
applications, where a large team of medical practitioners is needed
in close proximity to the patient, it may be desirable to place the
laser away from the operating table (e.g., in the corner of the
operating room, or in a different room entirely). In such
situations, a longer fiber may be desirable.
[0080] In general, photonic crystal fiber 120 is flexible, and can
be bent to relatively small radii of curvature over relatively
large angles without significantly impacting its performance (e.g.,
without causing the fiber to fail, or without reducing the fiber
transmission to a level where the system cannot be used for its
intended use while the fiber is bent). In some embodiments, an
operator can bend photonic crystal fiber 120 to have a relatively
small radius of curvature, such as about 15 cm or less (e.g., about
10 cm or less, about 8 cm or less, about 5 cm or less, about 3 cm
or less) while still delivering sufficient power to the target
location for the system to perform its function.
[0081] In general, the angle through which the fiber is bent can
vary, and usually depends on the procedure being performed. For
example, in some embodiments, the fiber can be bent through about
90.degree. or more (e.g., about 120.degree. or more, about
150.degree. or more).
[0082] Losses of transmitted power due to the operator bending
photonic crystal fiber 120 may be relatively small. In general,
losses due to bends should not significantly damage the fiber,
e.g., causing it to fail, or reduce the fiber output power to a
level where the system can no longer perform the function for which
it is designed. Embodiments of photonic crystal fiber 120 (e.g.,
about 1 meter or more in length) can be bent through 90.degree.
with a bend radius of about 5 centimeters or less, and still
transmit about 30% or more (e.g., about 50% or more, about 70% or
more) of radiation coupled into the fiber at the guided wavelength.
These fibers can provide such transmission characteristics and
provide average output power of about 3 Watts or more (e.g., about
5 Watts or more, about 8 Watts or more, about 10 Watts or
more).
[0083] The quality of the beam of the laser radiation emitted from
the output end of fiber 120 can be relatively good. For example,
the beam can have a low M.sup.2 value, such as about 4 or less
(e.g., about 3 or less, about 2.5 or less, about 2 or less).
M.sup.2 is a parameter commonly used to describe laser beam
quality, where an M.sup.2 value of about 1 corresponds to a
TEM.sub.00 beam emitted from a laser, which has a perfect Gaussian
profile. The M.sup.2 value is related to the minimum spot size that
can be formed from the beam according to the formula: d.sub.s=1.27
f.lamda.M.sup.2/d.sub.b (1) where d.sub.s is the minimum spot
diameter, d.sub.b is the beam diameter prior to being focused to
the spot by a lens having focal length f. Accordingly, the minimum
possible spot size a beam can be focused is proportional to the
M.sup.2 value for the beam. Practically, beams having smaller
values of M.sup.2 can provide higher radiation power densities to
the target area, with less damage to surrounding tissue due to the
decreased spot size.
[0084] The spot size of radiation delivered by photonic crystal
fiber 120 to the target tissue can be relatively small. For
example, in certain embodiments, the spot can have a diameter of
about 500 microns or less (e.g., about 300 microns or less, about
200 microns or less, such as about 100 microns) at a desired
working distance from the fiber's output end (e.g., from about 0.1
mm to about 3 mm). As discussed previously, a small spot size is
desirable where system 100 is being used to excise or incise tissue
or in other applications where substantial precision in the
delivery of the radiation is desired. Alternatively, in
applications where tissue is to be ablated or vaporized, and/or a
lesser level of precision is sufficient, the spot size can be
relatively large (e.g., having a diameter of about 2 millimeters or
more, about 3 millimeters or more, about 4 millimeters or
more).
[0085] While laser 110 is a CO.sub.2 laser, photonic crystal fibers
can be used in medical laser systems that use other types or
lasers, operating at wavelengths different from 10.6 microns. In
general, medical laser systems can provide radiation at ultraviolet
(UV), visible, or infrared (IR) wavelengths. Lasers delivering IR
radiation, for example, emit radiation having a wavelength between
about 0.7 microns and about 20 microns (e.g., between about 2 to
about 5 microns or between about 8 to about 12 microns). Waveguides
having hollow cores, such as photonic crystal fiber 120, are
well-suited for use with laser systems having wavelengths of about
2 microns or more, since gases that commonly occupy the core have
relatively low absorptions at these wavelengths compared to many
dielectric materials (e.g., silica-based glasses and various
polymers). In addition to CO.sub.2 lasers, other examples of lasers
which can emit IR radiation include Nd:YAG lasers (e.g., at 1.064
microns), Er:YAG lasers (e.g., at 2.94 microns), Er, Cr: YSGG
(Erbium, Chromium doped Yttrium Scandium Gallium Garnet) lasers
(e.g., at 2.796 microns), Ho:YAG lasers (e.g., at 2.1 microns),
free electron lasers (e.g., in the 6 to 7 micron range), and
quantum cascade lasers (e.g., in the 3 to 5 micron range).
[0086] In general, the type of laser used in a medical laser system
depends on the purpose for which the system is designed. The type
of laser can be selected depending on whether the system is to be
used in surgical procedures, in diagnosis, or in physiologic
studies. For example, an argon laser, which delivers in the blue
and green regions of the visible light spectrum, with two energy
peaks, at 488 nm and 514 nm, can be used for photocoagulation. A
dye laser, which is a laser with organic dye dissolved in a solvent
as the active medium whose beam is in the visible light spectrum,
can be used in photodynamic therapy. Excimer lasers provide
radiation in the ultraviolet spectrum, penetrates tissues only a
small distance, can be used to break chemical bonds of molecules in
tissue instead of generating heat to destroy tissue. Such lasers
can be used in ophthalmological procedures and laser angioplasty.
Ho:YAG lasers can provide radiation in the near infrared spectrum
and can be used for photocoagulation and photoablation. Krypton
lasers provide radiation in the yellow-red visible light spectrum,
and can be used for photocoagulation. Radiation from KTP lasers can
be frequency-doubled to provide radiation in the green visible
light spectrum and can be used for photoablation and
photocoagulation. Nd:YAG lasers can be for photocoagulation and
photoablation. Pulsed dye lasers can be used to provide in the
yellow visible light spectrum (e.g., with a wavelength of 577 nm or
585 nm), with alternating on and off phases of a few microseconds
each, and can be used to decolorize pigmented lesions.
[0087] In general, laser systems can use continuous wave or pulsed
lasers. Furthermore, while CO.sub.2 lasers are typically used at
average output powers of about 5 Watts to about 100 Watts, photonic
crystal fibers can generally be used with a variety of laser
powers. For example, average laser power can be in the milliwatt
range in certain systems, up to as much as several hundred Watts
(e.g., about 200 Watts or more) in extremely high power
systems.
[0088] In general, for high power systems, the average power
density guided by fiber 120 can be extremely high. For example,
power density in the fiber, or exiting the fiber's core, can be
about 10.sup.3 W/cm.sup.2 or more (e.g., about 10.sup.4 W/cm.sup.2
or more, about 10.sup.5 W/cm.sup.2 or more, 10.sup.6 W/cm2 or
more).
[0089] Referring to FIG. 2A, in general, photonic crystal fiber 120
includes a core 210, which is surrounded by a confinement region
220 extending along a waveguide axis 299 (normal to the plane of
FIG. 2A). Confinement region 220 is surrounded by a cladding 230
(e.g., a polymer cladding), which provides mechanical support and
protects the core and confinement region from environmental
hazards. Confinement region 220 includes a photonic crystal
structure that substantially confines radiation at a wavelength
.lamda. to core 210. Examples of such structures are described with
reference to FIGS. 2B-2D below. As used herein, a photonic crystal
is a structure (e.g., a dielectric structure) with a refractive
index modulation (e.g., a periodic refractive index modulation)
that produces a photonic bandgap in the photonic crystal. An
example of such a structure, giving rise to a one dimensional
refractive index modulation, is a stack of dielectric layers of
high and low refractive index, where the layers have substantially
the same optical thickness. A photonic bandgap, as used herein, is
a range of frequencies in which there are no accessible extended
(i.e., propagating, non-localized) states in the dielectric
structure. Typically the structure is a periodic dielectric
structure, but it may also include, e.g., more complex
"quasi-crystals." The bandgap can be used to confine, guide, and/or
localize light by combining the photonic crystal with "defect"
regions that deviate from the bandgap structure. Moreover, there
are accessible extended states for frequencies both below and above
the gap, allowing light to be confined even in lower-index regions
(in contrast to index-guided TIR structures). The term "accessible"
states means those states with which coupling is not already
forbidden by some symmetry or conservation law of the system. For
example, in two-dimensional systems, polarization is conserved, so
only states of a similar polarization need to be excluded from the
bandgap. In a waveguide with uniform cross-section (such as a
typical fiber), the wavevector .beta. is conserved, so only states
with a given .beta. need to be excluded from the bandgap to support
photonic crystal guided modes. Moreover, in a waveguide with
cylindrical symmetry, the "angular momentum" index m is conserved,
so only modes with the same m need to be excluded from the bandgap.
In short, for high-symmetry systems the requirements for photonic
bandgaps are considerably relaxed compared to "complete" bandgaps
in which all states, regardless of symmetry, are excluded.
[0090] Theoretically, a photonic crystal is only completely
reflective in the bandgap when the index modulation in the photonic
crystal has an infinite extent. Otherwise, incident radiation can
"tunnel" through the photonic crystal via an evanescent mode that
couples propagating modes on either side of the photonic crystal.
In practice, however, the rate of such tunneling decreases
exponentially with photonic crystal thickness (e.g., the number of
alternating layers). It also decreases with the magnitude of the
index contrast in the confinement region.
[0091] Furthermore, a photonic bandgap may extend over only a
relatively small region of propagation vectors. For example, a
dielectric stack may be highly reflective for a normally incident
ray and yet only partially reflective for an obliquely incident
ray. A "complete photonic bandgap" is a bandgap that extends over
all possible wavevectors and all polarizations. Generally, a
complete photonic bandgap is only associated with a photonic
crystal having index modulations along three dimensions. However,
in the context of EM radiation incident on a photonic crystal from
an adjacent dielectric material, we can also define an
"omnidirectional photonic bandgap," which is a photonic bandgap for
all possible wavevectors and polarizations for which the adjacent
dielectric material supports propagating EM modes. Equivalently, an
omnidirectional photonic bandgap can be defined as a photonic band
gap for all EM modes above the light line, wherein the light line
defines the lowest frequency propagating mode supported by the
material adjacent the photonic crystal. For example, in air the
light line is approximately given by .omega.=c.beta., where .omega.
is the angular frequency of the radiation, .beta. is the
wavevector, and c is the speed of light. A description of an
omnidirectional planar reflector is disclosed in U.S. Pat. No.
6,130,780, the entire contents of which are incorporated herein by
reference. Furthermore, the use of alternating dielectric layers to
provide omnidirectional reflection (in a planar limit) for a
cylindrical waveguide geometry is disclosed in Published PCT
application WO 00/22466, the contents of which are incorporated
herein by reference.
[0092] When confinement region 220 gives rise to an omnidirectional
bandgap with respect to core 210, the guided modes are strongly
confined because, in principle, any EM radiation incident on the
confinement region from the core is completely reflected. As
described above, however, such complete reflection only occurs when
there are an infinite number of layers. For a finite number of
layers (e.g., about 20 layers), an omnidirectional photonic bandgap
may correspond to a reflectivity in a planar geometry of at least
95% for all angles of incidence ranging from 0.degree. to
80.degree. and for all polarizations of EM radiation having
frequency in the omnidirectional bandgap. Furthermore, even when
fiber 120 has a confinement region with a bandgap that is not
omnidirectional, it may still support a strongly guided mode, e.g.,
a mode with radiation losses of less than 0.1 dB/km for a range of
frequencies in the band gap. Generally, whether or not the bandgap
is omnidirectional will depend on the size of the bandgap produced
by the alternating layer (which generally scales with index
contrast of the two layers) and the lowest-index constituent of the
photonic crystal.
[0093] Regarding the structure of photonic crystal fiber 120, in
general, the diameter of core 210 (indicated by reference numeral
211 in FIG. 2A) can vary depending on the end-use application of
system 100. For example, where a large spot size is desired, the
core can be relatively large (e.g., about 1 mm or more, about 2 mm
or more). Alternatively, when a small spot size is desired, core
diameter 211 can be much smaller (e.g., about 500 microns or less,
about 300 microns or less, about 200 microns or less, about 100
microns or less).
[0094] More generally, where fiber 120 is used in systems with
other types of laser, and/or used to guide wavelengths other than
10.6 microns, the core diameter depends on the wavelength or
wavelength range of the energy to be guided by the fiber, and on
whether the fiber is a single or multimode fiber. For example,
where the fiber is a single mode fiber for guiding visible
wavelengths (e.g., between about 400 nm and about 800 nm) the core
radius can be in the sub-micron to several micron range (e.g., from
about 0.5 microns to about 5 microns). However, the core radius can
be in the tens to thousands of microns range (e.g., from about 10
microns to about 2,000 microns, such as about 500 microns to about
1,000 microns), for example, where the fiber is a multimode fiber
for guiding IR wavelengths. The core radius can be about 5, or more
(e.g., about 10.lamda. or more, about 20.lamda. or more, about
50.lamda. or more, about 100.lamda. or more), where .lamda. is the
wavelength of the guided energy.
[0095] An advantage of photonic crystal fibers is that fibers
having small core diameters can be readily produced since fibers
can be drawn from a perform, preserving the relative proportions of
the fiber's cross-sectional structure while reducing the dimensions
of that structure to small sizes in a controlled manner.
[0096] In photonic crystal fiber 120, core 220 is hollow.
Alternatively, in embodiments where there are no fluids pumped
through the core, core 220 can include any material or combination
of materials that are Theologically compatible with the materials
forming confinement region 220 and that have sufficiently high
transmission properties at the guided wavelength(s). In some
embodiments, core 220 includes a dielectric material (e.g., an
amorphous dielectric material), such as an inorganic glass or a
polymer. In certain embodiments, core 220 can include one or more
dopant materials, such as those described in U.S. patent
application Ser. No. 10/121,452, entitled "HIGH INDEX-CONTRAST
FIBER WAVEGUIDES AND APPLICATIONS," filed Apr. 12, 2002 and now
published under Pub. No. US-2003-0044158-A1, the entire contents of
which are hereby incorporated by reference.
[0097] Cladding 230 can be formed from a polymer (e.g., an acrylate
or silicone polymer) or other material. Cladding 230 can be formed
from a material that is also used to as part of confinement region
220, which are described below. In applications where the cladding
comes in contact with a patient, it can be formed from materials
that conform to FDA standards for medical devices. In these
instances, silicone polymers, for example, may be particularly
suited for use as the cladding material. Typically, cladding 230
protects the fiber from external damage. By selecting the
appropriate thickness, composition, and/or structure, cladding 230
can also be designed to limit the flexibility of the fiber, e.g.,
to prevent damage by small radius of curvature bends.
[0098] In general, the thickness of fiber 120 can vary. The
thickness is indicated by outer diameter (OD) 231 in FIG. 2A. OD
231 can be selected so that fiber 120 is compatible with other
pieces of equipment. For example, fiber 120 can be made so that OD
231 is sufficiently small so that the fiber can be threaded through
a channel in an endoscope or other tool (e.g., OD 231 can be about
2,000 microns or less). In some embodiments, fiber 120 has a
relatively small OD (e.g., about 1,000 microns or less). Narrow
fibers can be useful in applications where they are to be inserted
into narrow spaces, such as through a patient's urethra.
Alternatively, in some embodiments, diameter 231 can be relatively
large compared (e.g., about 3,000 microns or more). Large OD's can
reduce the mechanical flexibility of the fiber, which can prevent
the fiber from bending to small radii of curvature that damage the
fiber or reduce its transmission to a level where the system can no
longer perform its intended function.
[0099] In addition to cladding 230, fiber 200 may include
additional components to limit bend radii. For example, the fiber
may include a spirally wound material around its outer diameter
(e.g., a spirally wound wire). Alternatively, or additionally, the
fiber may include additional claddings to provide additional
mechanical support.
[0100] Although the fiber can be bent (as discussed above), in some
embodiments, the fiber may be constrained from bending to radii of
curvature of less than about 20 cm (e.g., about 10 cm or less, 8 cm
or less, 5 cm or less) during regular use in the application for
which it is designed.
[0101] The cladding material may be selected so that the fiber is
sterilizable. For example, the cladding material may be selected so
that the fiber can withstand high temperatures (e.g., those
experienced in an autoclave).
[0102] Turning to the structure and composition of confinement
region 220, in some embodiments, photonic crystal fiber 120 is a
Bragg fiber and confinement region 220 includes multiple
alternating layers having high and low refractive indexes, where
the high and low index layers have similar optical thickness. For
example, referring to FIG. 2B, in some embodiments, confinement
region 220A includes multiple annular dielectric layers of
differing refractive index (i.e., layers composed of a high index
material having a refractive index n.sub.H, and layers composed of
a low index material having a refractive index n.sub.L), indicated
as layers 212, 213, 214, 215, 216, 217, 218, 219, 222, and 223.
Here, n.sub.H>n.sub.L and n.sub.H-n.sub.L can be, for example,
about 0.01 or more, about 0.05 or more, about 0.1 or more, about
0.2 or more, about 0.5 or more. For convenience, only a few of the
dielectric confinement layers are shown in FIG. 2B. In practice,
confinement region 220A may include many more layers (e.g., about
15 layers or more, about 20 layers or more, about 30 layers or
more, about 40 layers or more, about 50 layers or more, about 80
layers or more).
[0103] In some embodiments, confinement region 220 can give rise to
an omnidirectional bandgap with respect to core 210, wherein the
guided modes are strongly confined because, in principle, any EM
radiation incident on the confinement region from the core is
completely reflected. However, such complete reflection only occurs
when there are an infinite number of layers. For a finite number of
layers (e.g., about 20 layers), an omnidirectional photonic bandgap
may correspond to a reflectivity in a planar geometry of at least
95% for all angles of incidence ranging from 0.degree. to
80.degree. and for all polarizations of EM radiation having
frequency in the omnidirectional bandgap. Furthermore, even when
fiber 120 has a confinement region with a bandgap that is not
omnidirectional, it may still support a strongly guided mode, e.g.,
a mode with radiation losses of less than 0.1 dB/km for a range of
frequencies in the bandgap. Generally, whether or not the bandgap
is omnidirectional will depend on the size of the bandgap produced
by the alternating layers (which generally scales with index
contrast of the two layers) and the lowest-index constituent of the
photonic crystal.
[0104] The existence of an omnidirectional bandgap, however, may
not be necessary for useful application of fiber 120. For example,
in some embodiments, a laser beam used to establish the propagating
field in the fiber is a TEM.sub.00 mode. This mode can couple with
high efficiency to the HE.sub.11 mode of a suitably designed fiber.
Thus, for successful application of the fiber for transmission of
laser energy, it may only be necessary that the loss of this one
mode be sufficiently low. More generally, it may be sufficient that
the fiber support only a number of low loss modes (e.g., the
HE.sub.11 mode and the modes that couple to it from simple
perturbations, such as bending of the fiber). In other words,
photonic bandgap fibers may be designed to minimize the losses of
one or a group of modes in the fiber, without necessarily
possessing an omnidirectional bandgap.
[0105] For a planar dielectric reflector, it is well-known that,
for normal incidence, a maximum band gap is obtained for a
"quarter-wave" stack in which each layer has equal optical
thickness .lamda./4, or equivalently n hi .times. d hi = n lo
.times. d lo = .lamda. / 4 , ##EQU1## where d.sub.hi/lo and
n.sub.hi/lo refer to the thickness and refractive index,
respectively, of high-index and low-index layers in the stack.
Normal incidence, however, corresponds to .beta.=0, whereas for a
cylindrical waveguide the desired modes typically lie near the
light line .omega.=c.beta. (in the limit of large R, the
lowest-order modes are essentially plane waves propagating along
z-axis, i.e., the waveguide axis). In this case, the quarter-wave
condition becomes: d hi .times. n hi 2 - 1 = d lo .times. n lo 2 -
1 = .lamda. / 4 ( 2 ) ##EQU2##
[0106] This equation may not be exactly optimal because the
quarter-wave condition is modified by the cylindrical geometry,
which may require the optical thickness of each layer to vary
smoothly with its radial coordinate. In addition, the differing
absorption of the high and low index materials can change the
optimal layer thicknesses from their quarter-wave values.
[0107] In certain embodiments, confinement region 220 includes
layers that do not satisfy the quarter-wave condition given in Eq.
2. In other words, for the example shown in FIG. 2B, one or more of
layers 212, 213, 214, 215, 216, 217, 218, 219, 222, and 223 are
thicker or thinner than d.sub..lamda./4, where d .lamda. / 4 =
.lamda. 4 .times. n 2 - 1 , ##EQU3## and n is the refractive index
of the layer (i.e., d.sub..lamda./4 corresponds to an optical
thickness equal to the quarter-wave thickness). For example, one or
more layers in the confinement region can have a thickness of about
0.9 d.sub..lamda./4 or less (e.g., about 0.8 d.sub..lamda./4 or
less, about 0.7 d.sub..lamda./4 or less, about 0.6 d.sub..lamda./4
or about 0.5 d.sub..lamda./4 or less, about 0.4 d.sub..lamda./4 or
less, about 0.3 d.sub..lamda./4 or less), or about 1.1
d.sub..lamda./4 or more (e.g., about 1.2 d.sub..lamda./4 or more,
about 1.3 d.sub..lamda./4 or more, about 1.4 d.sub..lamda./4 or
more, about 1.5 d.sub..lamda./4 or more, about 1.8 d.sub..lamda./4
or more, about 2.0 d.sub..lamda./4 or more). In some embodiments,
all layers in the confinement region can be detuned from the
quarter-wave condition. In some embodiments, the thickness of one
or more of the high index layers can be different (e.g., thicker or
thinner) from the thickness of the other high index layers. For
example, the thickness of the innermost high index layer can be
different from the thickness of the other high index layers.
Alternatively, or additionally, the thickness of one or more of the
low index layers can be different (e.g., thicker or thinner) from
the thickness of the other low index layers. For example, the
thickness of the innermost low index layer can be different from
the thickness of the other low index layers.
[0108] Detuning the thickness of layers in the confinement region
from the quarter-wave condition can reduce the attenuation of
photonic crystal fiber 120 compared to a test fiber, which refers
to a fiber identical to photonic crystal fiber 120, except that the
quarter-wave condition is satisfied for all layers in the
confinement region (i.e., the test fiber has an identical core, and
its confinement region has the same number of layers with the same
composition as photonic crystal fiber 120). For example, fiber 120
can have an attenuation for one or more guided modes that is
reduced by a factor of about two or more compared to the
attenuation of the test fiber (e.g., reduced by a factor of about
three or more, about four or more, about five or more, about ten or
more, about 20 or more, about 50 or more, about 100 or more).
Examples of photonic crystal fibers illustrating reduce attenuation
are described in U.S. patent application Ser. No. 10/978,605,
entitled "PHOTONIC CRYSTAL WAVEGUIDES AND SYSTEMS USING SUCH
WAVEGUIDES," filed on Nov. 1, 2004, the entire contents of which is
hereby incorporated by reference.
[0109] The thickness of each layer in the confinement region can
vary depending on the composition and structure of the photonic
crystal fiber. Thickness can also vary depending on the wavelength,
mode, or group of modes for which the photonic crystal fiber is
optimized. The thickness of each layer can be determined using
theoretical and/or empirical methods. Theoretical methods include
computational modeling. One computational approach is to determine
the attenuation of a fiber for different layer thicknesses and use
an optimization routine (e.g., a non-linear optimization routine)
to determine the values of layer thickness that minimize the
fiber's attenuation for a guided mode. For example, the "downhill
simplex method", described in the text Numerical Recipes in FORTRAN
(second edition), by W. Press, S. Teukolsky, W. Vetterling, and B
Flannery, can be used to perform the optimization.
[0110] Such a model should account for different attenuation
mechanisms in a fiber. Two mechanisms by which energy can be lost
from a guided EM mode are by absorption loss and radiation loss.
Absorption loss refers to loss due to material absorption.
Radiation loss refers to energy that leaks from the fiber due to
imperfect confinement. Both modes of loss contribute to fiber
attenuation and can be studied theoretically, for example, using
transfer matrix methods and perturbation theory. A discussion of
transfer matrix methods can be found in an article by P. Yeh et
al., J. Opt. Soc. Am., 68, p. 1196 (1978). A discussion of
perturbation theory can found in an article by M. Skorobogatiy et
al., Optics Express, 10, p. 1227 (2002). Particularly, the transfer
matrix code finds propagation constants .beta. for the "leaky"
modes resonant in a photonic crystal fiber structure. Imaginary
parts of .beta.'s define the modal radiation loss, thus
Loss.sub.radiation.about.Im(.beta.). Loss due to material
absorption is calculated using perturbation theory expansions, and
in terms of the modal field overlap integral it can be determined
from Loss absorption .about. 2 .times. .pi..omega. .times. .intg. 0
.infin. .times. r .times. d r .function. ( .alpha. .times. .times.
E .fwdarw. .beta. * .times. E .fwdarw. .beta. ) , ( 3 ) ##EQU4##
where .omega. is the radiation frequency, r is the fiber radius,
.alpha. is bulk absorption of the material, and {right arrow over
(E)}.sub..beta. is an electric field vector.
[0111] Alternatively, the desired mode fields that can propagate in
the fiber can be expanded in a suitable set of functions, such as
B-splines (see, e.g., A Practical Guide to Splines, by C. deBoor).
Application of the Galerkin conditions (see, e.g., Computational
Galerkin Methods, C. A. J. Fletcher, Springer-Verlag, 1984) then
converts Maxwell's equations into a standard eigenvalue-eigenvector
problem, which can be solved using the LAPACK software package
(freely available, for example, from the netlib repository on the
internet, at "http://www.netlib.org"). The desired complex
propagation constants, containing both material and radiation
losses, are obtained directly from the eigenvalues.
[0112] Guided modes can be classified as one of three types: pure
transverse electric (TE); pure transverse magnetic (TM); and mixed
modes. Loss often depends on the type of mode. For example, TE
modes can exhibit lower radiation and absorption losses than
TM/mixed modes. Accordingly, the fiber can be optimized for guiding
a mode that experiences low radiation and/or absorption loss.
[0113] While confinement region 220A includes multiple annular
layers that give rise to a radial refractive index modulation, in
general, confinement regions can also include other structures to
provide confinement properties. For example, referring to FIG. 2C,
a confinement region 220B includes continuous layers 240 and 250 of
dielectric material (e.g., polymer, glass) having different
refractive indices, as opposed to multiple discrete, concentric
layers. Continuous layers 240 and 250 form a spiral around axis
299. One or more of the layers, e.g., layer 240 is a high-index
layer having an index n.sub.H and a thickness d.sub.H, and the
layer, e.g., layer 250, is a low-index layer having an index
n.sub.L and a thickness d.sub.L, where n.sub.H>n.sub.L (e.g.,
n.sub.H-n.sub.L can be about 0.01 or more, about 0.05 or more,
about 0.1 or more, about 0.2 or more, about 0.5 or more).
[0114] Because layers 240 and 250 spiral around axis 199, a radial
section extending from axis 199 intersects each of the layers more
than once, providing a radial profile that includes alternating
high index and low index layers.
[0115] The spiraled layers in confinement region 220B provide a
periodic variation in the index of refraction along a radial
section, with a period corresponding to the optical thickness of
layers 240 and 250. In general, the radial periodic variation has
an optical period corresponding to
n.sub.240d.sub.240+n.sub.250d.sub.250.
[0116] The thickness (d.sub.240 and d.sub.250) and optical
thickness (n.sub.240d.sub.240 and n.sub.250d.sub.250) of layers 240
and 250 are selected based on the same considerations as discussed
for confinement region 220A above.
[0117] For the embodiment shown in FIG. 2C, confinement region 220B
is 5 optical periods thick. In practice, however, spiral
confinement regions may include many more optical periods (e.g.,
about 8 optical periods or more, about 10 optical periods or more,
about 15 optical periods or more, about 20 optical periods or more,
about 25 optical periods or more, such as about 40 or more optical
periods).
[0118] Fiber's having spiral confinement regions can be formed from
a spiral perform by rolling a planar multilayer film into a spiral
and consolidating the spiral by fusing (e.g., by heating) the
adjacent layers of the spiral together. In some embodiments, the
planar multilayer film can be rolled into a spiral around a mandrel
(e.g., a glass cylinder or rod), and the mandrel can be removed
(e.g., by etching or by separating the mandrel from the spiral
sheath and slipping it out of the sheath) after consolidation to
provide the spiral cylinder. The mandrel can be formed from a
single material, or can include portions of different materials.
For example, in some embodiments, the mandrel can be coated with
one or more layers that are not removed after consolidation of the
rolled spiral structure. As an example, a mandrel can be formed
from a first material (e.g., a silicate glass) in the form of a
hollow rod, and a second material (e.g., another glass, such as a
chalcogenide glass) coated onto the outside of the hollow rod. The
second material can be the same as one of the materials used to
form the multilayer film. After consolidation, the first material
is etched, and the second material forms part of the fiber
preform.
[0119] In some embodiments, additional material can be disposed on
the outside of the wrapped multilayer film. For example, a polymer
film can be wrapped around the outside of the spiral, and
subsequently fused to the spiral to provide an annular polymer
layer (e.g., the cladding). In certain embodiments, both the
multilayer film and an additional film can be wrapped around the
mandrel and consolidated in a single fusing step. In embodiments,
the multilayer film can be wrapped and consolidated around the
mandrel, and then the additional film can be wrapped around the
fused spiral and consolidated in a second fusing step. The second
consolidation can occur prior to or after etching the mandrel.
Optionally, one or more additional layers can be deposited (e.g.,
using CVD) within the spiral prior to wrapping with the additional
film.
[0120] Methods for preparing spiral articles are described in U.S.
patent application Ser. No. 10/733,873, entitled "FIBER WAVEGUIDES
AND METHODS OF MAKING SAME," filed on Dec. 10, 2003, the entire
contents of which are hereby incorporated by reference.
[0121] Referring to FIG. 2D, in some embodiments, photonic crystal
fiber 120 can include a confinement region 220C that includes a
spiral portion 260 and an annular portion 270. The number of layers
in annular portion 270 and spiral portion 260 (along a radial
direction from the fiber axis) can vary as desired. In some
embodiments, annular portion can include a single layer.
Alternatively, as shown in FIG. 2D, annular portion 270 can include
multiple layers (e.g., two or more layers, three or more layers,
four or more layers, five or more layers, ten or more layers).
[0122] In embodiments where annular portion 270 includes more than
one layer, the optical thickness of each layer may be the same or
different as other layers in the annular portion. In some
embodiments, one or more of the layers in annular portion 270 may
have an optical thickness corresponding to the quarter wave
thickness (i.e., as given by Eq. (2). Alternatively, or
additionally, one or more layers of annular portion 270 can have a
thickness different from the quarter wave thickness. Layer
thickness can be optimized to reduce (e.g., minimize) attenuation
of guided radiation using the optimization methods disclosed
herein.
[0123] In certain embodiments, annular portion 270 can be formed
from materials that have relatively low concentrations of defects
that would scatter and/or absorb radiation guided by photonic
crystal fiber 120. For example, annular portion 270 can include one
or more glasses with relatively low concentrations of
inhomogeneities and/or impurities. Inhomogeneities and impurities
can be identified using optical or electron microscopy, for
example. Raman spectroscopy, glow discharge mass spectroscopy,
sputtered neutrals mass spectroscopy or Fourier Transform Infrared
spectroscopy (FTIR) can also be used to monitor inhomogeneities
and/or impurities in photonic crystal fibers.
[0124] In certain embodiments, annular portion 270 is formed from
materials with a lower concentration of defects than spiral portion
260. In general, these defects include both structural defects
(e.g., delamination between layers, cracks) and material
inhomogeneities (e.g., variations in chemical composition and/or
crystalline structure).
[0125] Fibers having confinement regions such as shown in FIG. 2D
can be prepared by depositing one or more annular layers onto a
surface of a cylinder having a spiral cross-section to form a
preform. The photonic crystal fiber can then be drawn from the
preform.
[0126] Annular layers can be deposited onto a surface of the spiral
cylinder using a variety of deposition methods. For example, where
the spiral portion is between the annular portion and the core,
material can be evaporated or sputtered onto the outer surface of
the spiral article to form the preform.
[0127] In embodiments where the annular portion of the photonic
crystal fiber is between the spiral portion and the core, material
can be deposited on the inner surface of the spiral article by, for
example, chemical vapor deposition (e.g., plasma enhanced chemical
vapor deposition). Methods for depositing layers of, for example,
one or more glasses onto an inner surface of a cylindrical preform
are described in U.S. patent application Ser. No. 10/720,453,
entitled "DIELECTRIC WAVEGUIDE AND METHOD OF MAKING THE SAME,"
filed on Nov. 24, 2003, the entire contents of which are hereby
incorporated by reference.
[0128] In general, a confinement region may include photonic
crystal structures different from a multilayer configuration. For
example, confinement region 220C includes both a spiral portion and
annular portion, in some embodiments, confinement regions can
include portions with other non-spiral structure. For example, a
confinement region can include a spiral portion and a holey portion
(e.g., composed of a solid cylinder perforated by a number of holes
that extend along the fiber's axis). The holes can be arranged
along concentric circles, providing a variation in the radial
refractive index of the holey portion of the confinement
region.
[0129] With regard to the composition of confinement region 220,
the composition of high index and low index layers are typically
selected to provide a desired refractive index contrast between the
layers at the fiber's operational wavelength(s). The composition of
each high index layer can be the same or different as other high
index layers, just as the composition of each low index layer can
be the same or different as other low index layers.
[0130] Suitable materials for high and low index layers can include
inorganic materials such as inorganic glasses or amorphous alloys.
Examples of inorganic glasses include oxide glasses (e.g., heavy
metal oxide glasses), halide glasses and/or chalcogenide glasses,
and organic materials, such as polymers. Examples of polymers
include acrylonitrile-butadiene-styrene (ABS), poly
methylmethacrylate (PMMA), cellulose acetate butyrate (CAB),
polycarbonates (PC), polystyrenes (PS) (including, e.g., copolymers
styrene-butadiene (SBC), methylestyrene-acrylonitrile,
styrene-xylylene, styrene-ethylene, styrene-propylene,
styrene-acylonitrile (SAN)), polyetherimide (PEI), polyvinyl
acetate (PVAC), polyvinyl alcohol (PVA), polyvinyl chloride (PVC),
polyoxymethylene; polyformaldehyde (polyacetal) (POM), ethylene
vinyl acetate copolymer (EVAC), polyamide (PA), polyethylene
terephthalate (PETP), fluoropolymers (including, e.g.,
polytetrafluoroethylene (PTFE), polyperfluoroalkoxythylene (PFA),
fluorinated ethylene propylene (FEP)), polybutylene terephthalate
(PBTP), low density polyethylene (PE), polypropylene (PP), poly
methyl pentenes (PMP) (and other polyolefins, including cyclic
polyolefins), polytetrafluoroethylene (PTFE), polysulfides
(including, e.g., polyphenylene sulfide (PPS)), and polysulfones
(including, e.g., polysulfone (PSU), polyehtersulfone (PES),
polyphenylsulphone (PPSU), polyarylalkylsulfone, and
polysulfonates). Polymers can be homopolymers or copolymers (e.g.,
(Co)poly(acrylamide-acrylonitrile) and/or acrylonitrile styrene
copolymers). Polymers can include polymer blends, such as blends of
polyamides-polyolefins, polyamides-polycarbonates, and/or
PES-polyolefins, for example.
[0131] Further examples of polymers that can be used include cyclic
olefin polymers (COPs) and cyclic olefin copolymers (COCs). In some
embodiments, COPs and COCs can be prepared by polymerizing
norbornen monomers or copolymerization norbomen monomers and other
polyolefins (polyethylene, polypropylene). Commercially-available
COPs and/or COCs can be used, including, for example, Zeonex.RTM.
polymers (e.g., Zeonex.RTM. E48R) and Zeonor.RTM. copolymers (e.g.,
Zeonor.RTM. 1600), both available from Zeon Chemicals L.P.
(Louisville, Ky.). COCs can also be obtained from Promerus LLC
(Brecksville, Ohio) (e.g., such as FS1700).
[0132] Alternatively, or additionally, low-index regions may be
fabricated by using hollow structural support materials, such as
silica spheres or hollow fibers, to separate high-index layers or
regions. Examples of fibers that include such structural supports
are described in Published International Application WO 03/058308,
entitled "BIREFRINGENT OPTICAL FIBRES," the entire contents of
which are hereby incorporated by reference.
[0133] In certain embodiments, the confinement region is a
dielectric confinement region, being composed of substantially all
dielectric materials, such as one or more glasses and/or one or
more dielectric polymers. Generally, a dielectric confinement
region includes substantially no metal layers.
[0134] In some embodiments, the high index layers or low index
layers of the confinement region can include chalcogenide glasses
(e.g., glasses containing a chalcogen element, such as sulphur,
selenium, and/or tellurium). In addition to a chalcogen element,
chalcogenide glasses may include one or more of the following
elements: boron, aluminum, silicon, phosphorus, sulfur, gallium,
germanium, arsenic, indium, tin, antimony, thallium, lead, bismuth,
cadmium, lanthanum and the halides (fluorine, chlorine, bromide,
iodine).
[0135] Chalcogenide glasses can be binary or ternary glasses, e.g.,
As--S, As--Se, Ge--S, Ge--Se, As--Te, Sb--Se, As--S--Se, S--Se--Te,
As--Se--Te, As--S--Te, Ge--S--Te, Ge--Se--Te, Ge--S--Se,
As--Ge--Se, As--Ge--Te, As--Se--Pb, As--S--Tl, As--Se--Tl,
As--Te--Tl, As--Se--Ga, Ga--La--S, Ge--Sb--Se or complex,
multi-component glasses based on these elements such as
As--Ga--Ge--S, Pb--Ga--Ge--S, etc. The ratio of each element in a
chalcogenide glass can be varied.
[0136] In certain embodiments, in addition or alternative to
chalcogenide glass(es), one or more layers in confinement region
220 can include one or more oxide glasses (e.g., heavy metal oxide
glasses), halide glasses, amorphous alloys, or combinations
thereof.
[0137] In general, the absorption of the high and low index layers
varies depending on their composition and on the fiber's
operational wavelength(s). In some embodiments, the material
forming both the high and low index layers can have low absorption.
A low absorption material has absorption of about 100 dB/m or less
at the wavelength of operation (e.g., about 20 dB/m or less, about
10 dB/m or less, about 5 dB/m or less, about 1 dB/m or less, 0.1
dB/m or less). Examples of low absorption materials include
chalcogenide glasses, which, at wavelengths of about 3 microns,
exhibit an absorption coefficient of about 4 dB/m. At wavelengths
of about 10.6 microns, chalcogenide glasses exhibit an absorption
coefficient of about 10 dB/m. As another example, oxide glasses
(e.g., lead borosilicate glasses, or silica) can have low
absorption for wavelengths between about 1 and 2 microns. Some
oxide glasses can have an absorption coefficient of about 1 dB/m to
0.0002 dB/m in this wavelength range.
[0138] Alternatively, one or both of the high and low index
materials can have high absorption (e.g., about 100 dB/m or more,
such as about 1,000 or more, about 10,000 or more, about 20,000 or
more, about 50,000 dB/m or more). For example, many polymers
exhibit an absorption coefficient of about 10.sup.5 dB/m for
wavelengths between about 3 and about 11 microns. Examples of such
polymers include polyetherimide (PEI), polychlorotrifluoro ethylene
(PCTFE), perfluoroalkoxyethylene (PFA), and polyethylene
naphthalate (PEN). PEI has an absorption of more than about
10.sup.5 dB/m at 3 microns, while PCTFE, PFA, and PEN have
absorptions of more than about 10.sup.5 dB/m at 10.6 microns.
[0139] In some embodiments, the high index material has a low
absorption coefficient and the low absorption material has a high
absorption coefficient, or vice versa.
[0140] A material's absorption can be determined by measuring the
relative transmission through at least two different thicknesses,
T.sub.1 and T.sub.2, of the material. Assuming the field in the
material decays with thickness T according to Pe.sup.-.alpha.T,
with P representing the power incident on the material, the
measured transmitted power through thicknesses T.sub.1 and T.sub.2
will then be P.sub.1=Pe.sup.-.alpha.T and
P.sub.2=Pe.sup.-.alpha.T.sub.2. The absorption coefficient .alpha.
is thenobtained as .alpha. = - 1 T 2 - T 1 .times. ln .function. (
P 2 / P 1 ) . ##EQU5## If desired, a more accurate evaluation of
.alpha. can be obtained by using several thicknesses and performing
a least squares fit to the logarithm of the transmitted power.
[0141] As discussed previously, materials can be selected for the
confinement region to provide advantageous optical properties
(e.g., low absorption with appropriate indices of refraction at the
guided wavelength(s)). However, the materials should also be
compatible with the processes used to manufacture the fiber. In
some embodiments, the high and low index materials should
preferably be compatible for co-drawing. Criteria for co-drawing
compatibility are provided in aforementioned U.S. patent
application Ser. No. 10/121,452, entitled "HIGH INDEX-CONTRAST
FIBER WAVEGUIDES AND APPLICATIONS." In addition, the high and low
index materials should preferably be sufficiently stable with
respect to crystallization, phase separation, chemical attack and
unwanted reactions for the conditions (e.g., environmental
conditions such as temperature, humidity, and ambient gas
environment) under which the fiber is formed, deployed, and
used.
[0142] When making a robust fiber waveguides using a drawing
process, not every combination of materials with desired optical
properties is necessarily suitable. Typically, one should select
materials that are rheologically, thermo-mechanically, and
physico-chemically compatible. Several criteria for selecting
compatible materials will now be discussed.
[0143] A first criterion is to select materials that are
rheologically compatible. In other words, one should select
materials that have similar viscosities over a broad temperature
range, corresponding to the temperatures experience during the
different stages of fiber drawing and operation. Viscosity is the
resistance of a fluid to flow under an applied shear stress. Here,
viscosities are quoted in units of Poise. Before elaborating on
Theological compatibility, it is usefule define a set of
characteristic temperatures for a given material, which are
temperatures at which the given material has a specific
viscosity.
[0144] The annealing point, T.sub..alpha., is the temperature at
which a material has a viscosity 10.sup.13 Poise. T.sub..alpha.can
be measured using a Model SP-2A System from Orton Ceramic
Foundation (Westerville, Ohio). Typically, T.sub..alpha. is the
temperature at which the viscosity of a piece of glass is low
enough to allow for relief of residual stresses.
[0145] The softening point, T.sub.s, is the temperature at which a
material has a viscosity 10.sup.7.65 Poise. T.sub.s can be measured
using a softening point instrument, e.g., Model SP-3A from Orton
Ceramic Foundation (Westerville, Ohio). The softening point is
related to the temperature at which the materials flow changes from
plastic to viscous in nature.
[0146] The working point, T.sub.w, is the temperature at which a
material has a viscosity 10.sup.4 Poise. T.sub.w can be measured
using a glass viscometer, e.g., Model SP-4A from Orton Ceramic
Foundation (Westerville, Ohio). The working point is related to the
temperature at which a glass can be easily drawn into a fiber. In
some embodiments, for example, where the material is an inorganic
glass, the material's working point temperature can be greater than
250.degree. C., such as about 300.degree. C., 400.degree. C.,
500.degree. C. or more.
[0147] The melting point, T.sub.m, is the temperature at which a
material has a viscosity 10.sup.2 Poise. T.sub.m can also be
measured using a glass viscometer, e.g., Model SP-4A from Orton
Ceramic Foundation (Westerville, Ohio). The melting point is
related to the temperature at which a glass becomes a liquid and
control of the fiber drawing process with respect to geometrical
maintenance of the fiber becomes very difficult.
[0148] To be Theologically compatible, two materials should have
similar viscosities over a broad temperature range, e.g., from the
temperature at which the fiber is drawn down to the temperature at
which the fiber can no longer release stress at a discernible rates
(e.g., at T.sub..alpha.) or lower. Accordingly, the working
temperature of two compatible materials should be similar, so that
the two materials flow at similar rates when drawn. For example, if
one measures the viscosity of the first material, .eta..sub.1(T) at
the working temperature of the second material, T.sub.w2,
.eta..sub.1(T.sub.w2) should be at least 10.sup.3 Poise, e.g.,
10.sup.4 Poise or 10.sup.5 Poise, and no more than 10.sup.7 Poise.
Moreover, as the drawn fiber cools the behavior of both materials
should change from viscous to elastic at similar temperatures. In
other words, the softening temperature of the two materials should
be similar. For example, at the softening temperature of the second
material, T.sub.s2, the viscosity of the first material,
.eta..sub.1(T.sub.s2) should be at least 10.sup.6 Poise, e.g.,
10.sup.7 Poise or 10.sup.8 Poise and no more than 10.sup.9 Poise.
In preferred embodiments, it should be possible to anneal both
materials together, so at the annealing temperature of the second
material, T.sub.a2, the viscosity of the first material,
.eta..sub.1(T.sub.a2) should be at least 10.sup.8 Poise (e.g., at
least 10.sup.9 Poise, at least 10.sup.10 Poise, at least 10.sup.11
Poise, at least 10.sup.12 Poise, at least 10.sup.13 Poise, at least
10.sup.14 Poise).
[0149] Additionally, to be Theologically compatible, the change in
viscosity as a function of temperature (i.e., the viscosity slope)
for both materials should preferably match as close as
possible.
[0150] A second selection criterion is that the thermal expansion
coefficients (TEC) of each material should be similar at
temperatures between the annealing temperatures and room
temperature. In other words, as the fiber cools and its rheology
changes from liquid-like to solid-like, both materials' volume
should change by similar amounts. If the two materials TEC's are
not sufficiently matched, a large differential volume change
between two fiber portions can result in a large amount of residual
stress buildup, which can cause one or more portions to crack
and/or delaminate. Residual stress may also cause delayed fracture
even at stresses well below the material's fracture stress.
[0151] The TEC is a measure of the fractional change in sample
length with a change in temperature. This parameter can be
calculated for a given material from the slope of a
temperature-length (or equivalently, temperature-volume) curve. The
temperature-length curve of a material can be measured using e.g.,
a dilatometer, such as a Model 1200D dilatometer from Orton Ceramic
Foundation (Westerville, Ohio). The TEC can be measured either over
a chosen temperature range or as the instantaneous change at a
given temperature. This quantity has the units .degree.
C..sup.-1.
[0152] For many materials, there are two linear regions in the
temperature-length curve that have different slopes. There is a
transition region where the curve changes from the first to the
second linear region. This region is associated with a glass
transition, where the behavior of a glass sample transitions from
that normally associated with a solid material to that normally
associated with a viscous fluid. This is a continuous transition
and is characterized by a gradual change in the slope of the
temperature-volume curve as opposed to a discontinuous change in
slope. A glass transition temperature, T.sub.g, can be defined as
the temperature at which the extrapolated glass solid and viscous
fluid lines intersect. The glass transition temperature is a
temperature associated with a change in the materials rheology from
a brittle solid to a solid that can flow. Physically, the glass
transition temperature is related to the thermal energy required to
excite various molecular translational and rotational modes in the
material. The glass transition temperature is often taken as the
approximate annealing point, where the viscosity is 10.sup.13
Poise, but in fact, the measured T.sub.g is a relative value and is
dependent upon the measurement technique.
[0153] A dilatometer can also be used to measure a dilatometric
softening point, T.sub.ds. A dilatometer works by exerting a small
compressive load on a sample and heating the sample. When the
sample temperature becomes sufficiently high, the material starts
to soften and the compressive load causes a deflection in the
sample, when is observed as a decrease in volume or length. This
relative value is called the dilatometric softening point and
usually occurs when the materials viscosity is between 10.sup.10
and 10.sup.12.5 Poise. The exact T.sub.ds value for a material is
usually dependent upon the instrument and measurement parameters.
When similar instruments and measurement parameters are used, this
temperature provides a useful measure of different materials
rheological compatibility in this viscosity regime.
[0154] As mentioned above, matching the TEC is an important
consideration for obtaining fiber that is free from excessive
residual stress, which can develop in the fiber during the draw
process. Typically, when the TEC's of the two materials are not
sufficiently matched, residual stress arises as elastic stress. The
elastic stress component stems from the difference in volume
contraction between different materials in the fiber as it cools
from the glass transition temperature to room temperature (e.g.,
25.degree. C.). The volume change is determined by the TEC and the
change in temperature. For embodiments in which the materials in
the fiber become fused or bonded at any interface during the draw
process, a difference in their respective TEC's will result in
stress at the interface. One material will be in tension (positive
stress) and the other in compression (negative stress), so that the
total stress is zero. Moderate compressive stresses themselves are
not usually a major concern for glass fibers, but tensile stresses
are undesirable and may lead to failure over time. Hence, it is
desirable to minimize the difference in TEC's of component
materials to minimize elastic stress generation in a fiber during
drawing. For example, in a composite fiber formed from two
different materials, the absolute difference between the TEC's of
each glass between T.sub.g and room temperature measured with a
dilatometer with a heating rate of 3.degree. C./min, should be no
more than about 5.times.10.sup.-6 .degree. C..sup.-1 (e.g., no more
than about 4.times.10.sup.-6 .degree. C..sup.-1, no more than about
3.times.10.sup.-6 .degree. C..sup.-1, no more than about
2.times.10.sup.-6 .degree. C..sup.-1, no more than about
1.times.10.sup.-6 .degree. C..sup.-1, no more than about
5.times.10.sup.-7 .degree. C..sup.-1, no more than about
4.times.10.sup.-7 .degree. C..sup.-1, no more than about
3.times.10.sup.-7 .degree. C..sup.-1, no more than about
2.times.10.sup.-7 .degree. C..sup.-1).
[0155] While selecting materials having similar TEC's can minimize
an elastic stress component, residual stress can also develop from
viscoelastic stress components. A viscoelastic stress component
arises when there is sufficient difference between strain point or
glass transition temperatures of the component materials. As a
material cools below T.sub.g it undergoes a sizeable volume
contraction. As the viscosity changes in this transition upon
cooling, the time needed to relax stress increases from zero
(instantaneous) to minutes. For example, consider a composite
preform made of a glass and a polymer having different glass
transition ranges (and different T.sub.g's). During initial
drawing, the glass and polymer behave as viscous fluids and
stresses due to drawing strain are relaxed instantly. After leaving
the hottest part of the draw furnace, the fiber rapidly loses heat,
causing the viscosities of the fiber materials to increase
exponentially, along with the stress relaxation time. Upon cooling
to its T.sub.g, the glass and polymer cannot practically release
any more stress since the stress relaxation time has become very
large compared with the draw rate. So, assuming the component
materials possess different T.sub.g values, the first material to
cool to its T.sub.g can no longer reduce stress, while the second
material is still above its T.sub.g and can release stress
developed between the materials. Once the second material cools to
its T.sub.g, stresses that arise between the materials can no
longer be effectively relaxed. Moreover, at this point the volume
contraction of the second glass is much greater than the volume
contraction of the first material (which is now below its T.sub.g
and behaving as a brittle solid). Such a situation can result
sufficient stress buildup between the glass and polymer so that one
or both of the portions mechanically fail. This leads us to a third
selection criterion for choosing fiber materials: it is desirable
to minimize the difference in T.sub.g's of component materials to
minimize viscoelastic stress generation in a fiber during drawing.
Preferably, the glass transition temperature of a first material,
T.sub.g1, should be within 100.degree. C. of the glass transition
temperature of a second material, T.sub.g2 (e.g.,
|T.sub.g1-T.sub.g2| should be less than 90.degree. C., less than
80.degree. C., less than 70.degree. C., less than 60.degree. C.,
less than 50.degree. C., less than 40.degree. C., less than
30.degree. C., less than 20.degree. C., less than 10.degree.
C.).
[0156] Since there are two mechanisms (i.e., elastic and
viscoelastic) to develop permanent stress in drawn fibers due to
differences between constituent materials, these mechanisms may be
employed to offset one another. For example, materials constituting
a fiber may naturally offset the stress caused by thermal expansion
mismatch if mismatch in the materials T.sub.g's results in stress
of the opposite sign. Conversely, a greater difference in T.sub.g
between materials is acceptable if the materials' thermal expansion
will reduce the overall permanent stress. One way to assess the
combined effect of thermal expansion and glass transition
temperature difference is to compare each component materials'
temperature-length curve. After finding T.sub.g for each material
using the foregoing slope-tangent method, one of the curves is
displaced along the ordinate axis such that the curves coincide at
the lower T.sub.g temperature value. The difference in y-axis
intercepts at room temperature yields the strain, .epsilon.,
expected if the glasses were not conjoined. The expected tensile
stress, .sigma., for the material showing the greater amount of
contraction over the temperature range from T.sub.g to room
temperature, can be computed simply from the following equation:
.sigma.=E.epsilon. (4) where E is the elastic modulus for that
material. Typically, residual stress values less than about 100 MPa
(e.g., about 50 MPa or less, about 30 MPa or less), are
sufficiently small to indicate that two materials are compatible. A
fourth selection criterion is to match the thermal stability of
candidate materials. A measure of the thermal stability is given by
the temperature interval (T.sub.x-T.sub.g), where T.sub.x is the
temperature at the onset of the crystallization as a material cools
slowly enough that each molecule can find its lowest energy state.
Accordingly, a crystalline phase is a more energetically favorable
state for a material than a glassy phase. However, a material's
glassy phase typically has performance and/or manufacturing
advantages over the crystalline phase when it comes to fiber
waveguide applications. The closer the crystallization temperature
is to the glass transition temperature, the more likely the
material is to crystallize during drawing, which can be detrimental
to the fiber (e.g., by introducing optical inhomogeneities into the
fiber, which can increase transmission losses). Usually a thermal
stability interval, (T.sub.x-T.sub.g) of at least about 80.degree.
C. (e.g., at least about 100.degree. C.) is sufficient to permit
fiberization of a material by drawing fiber from a preform. In
preferred embodiments, the thermal stability interval is at least
about 120.degree. C., such as about 150.degree. C. or more, such as
about 200.degree. C. or more. T.sub.x can be measured using a
thermal analysis instrument, such as a differential thermal
analyzer (DTA) or a differential scanning calorimeter (DSC).
[0157] A further consideration when selecting materials that can be
co-drawn are the materials' melting temperatures, T.sub.m. At the
melting temperature, the viscosity of the material becomes too low
to successfully maintain precise geometries during the fiber draw
process. Accordingly, in preferred embodiments the melting
temperature of one material is higher than the working temperature
of a second, rheologically compatible material. In other words,
when heating a preform, the preform reaches a temperature at it can
be successfully drawn before either material in the preform
melts.
[0158] One example of a pair of materials which can be co-drawn and
which provide a photonic crystal fiber waveguide with high index
contrast between layers of the confinement region are
As.sub.2Se.sub.3 and the polymer PES. As.sub.2Se.sub.3 has a glass
transition temperature (T.sub.g) of about 180.degree. C. and a
thermal expansion coefficient (TEC) of about
24.times.10.sup.-6/.degree. C. At 10.6 .mu.m, As.sub.2Se.sub.3 has
a refractive index of 2.7775, as measured by Hartouni and coworkers
and described in Proc. SPIE, 505, 11 (1984), and an absorption
coefficient, cc, of 5.8 dB/m, as measured by Voigt and Linke and
described in "Physics and Applications of Non-Crystalline
Semiconductors in Optoelectronics," Ed. A. Andriesh and M.
Bertolotti, NATO ASI Series, 3. High Technology, Vol. 36, p. 155
(1996). Both of these references are hereby incorporated by
reference in their entirety. PES has a TEC of about
55.times.10.sup.-6/.degree. C. and has a refractive index of about
1.65.
[0159] Embodiments of photonic crystal fibers and methods for
forming photonic crystal fibers are described in the following
patents and patent applications: U.S. Pat. No. 6,625,364, entitled
"LOW-LOSS PHOTONIC CRYSTAL WAVEGUIDE HAVING LARGE CORE RADIUS;"
U.S. Pat. No. 6,563,981, entitled "ELECTROMAGNETIC MODE CONVERSION
IN PHOTONIC CRYSTAL MULTIMODE WAVEGUIDES;" U.S. patent application
Ser. No. 10/057,440, entitled "PHOTONIC CRYSTAL OPTICAL WAVEGUIDES
HAVING TAILORED DISPERSION PROFILES," and filed on Jan. 25, 2002;
U.S. patent application Ser. No. 10/121,452, entitled "HIGH
INDEX-CONTRAST FIBER WAVEGUIDES AND APPLICATIONS," and filed on
Apr. 12, 2002; U.S. Pat. No. 6,463,200, entitled "OMNIDIRECTIONAL
MULTILAYER DEVICE FOR ENHANCED OPTICAL WAVEGUIDING;" Provisional
60/428,382, entitled "HIGH POWER WAVEGUIDE," and filed on Nov. 22,
2002; U.S. patent application Ser. No. 10/196,403, entitled "METHOD
OF FORMING REFLECTING DIELECTRIC MIRRORS," and filed on Jul. 16,
2002; U.S. patent application Ser. No. 10/720,606, entitled
"DIELECTRIC WAVEGUIDE AND METHOD OF MAKING THE SAME," and filed on
Nov. 24, 2003; U.S. patent application Ser. No. 10/733,873,
entitled "FIBER WAVEGUIDES AND METHODS OF MAKING SAME," and filed
on Dec. 10, 2003. The contents of each of the above mentioned
patents and patent applications are hereby incorporated by
reference in their entirety.
[0160] Referring again to FIG. 1, in some embodiments, photonic
crystal fiber 120 can be can be designed so that the fiber bends
preferably in a certain plane. For example, referring to FIG. 3, a
photonic crystal fiber 300 includes a cladding 360 that has an
asymmetric cross-section with a larger diameter along a major axis
361 compared to its diameter along a minor axis 362 orthogonal to
the major axis. The major and minor axes are orthogonal to axis
399. The asymmetric cross-section is also manifested in the shape
of the cladding's outer surface, which includes portions of
differing curvature. In particular, cladding 360 includes arcuate
portions 331 and 332 and two straight portions 333 and 334. Arcuate
portions 331 and 332 are on opposite sides of the cladding along
major axis 321. Straight portions 333 and 334 are on opposite sides
of the cladding along minor axis 322.
[0161] In general, the asymmetry of the cross-sectional profile of
cladding 360 is sufficient to cause fiber 300 to preferably bend in
a plane defined by fiber axis 399 and the minor axis 362 during
normal use of the fiber.
[0162] The ratio of fiber 300's diameter along the major axis to
its diameter along the minor axis can vary. Typically, this ration
is selected so that fiber 300 bends preferably in the bend plane,
while cladding 300 still provides the desired mechanical support or
other function(s) for which it is designed (e.g., optical function,
thermal management). In some embodiments, this ratio can be
relatively low, such as about 1.5:1 or less (e.g., about 1.3:1 or
less, about 1.1:1 or less). Alternatively, in certain embodiments,
this ratio can be larger than about 1.5:1 (e.g., about 1.8:1 or
more, about 2:1 or more).
[0163] Photonic crystal fiber 300 also includes a core 320 and a
confinement region 310 that includes spiral layers 330, 340, and
350, and has an inner seam 321 and an outer seam 322 corresponding
to the edges of the continuous layers from which the confinement
region is formed. Inner seam 321 is located along an azimuth 323
that is displaced by an angle a from minor axis 362. .alpha. can be
about 10.degree. or more (e.g., about 20.degree. or more, about
30.degree. or more, about 40.degree. or more, about 50.degree. or
more, about 60.degree. or more, about 70.degree. or more, about
80.degree. or more). In some embodiments, .alpha. is about
90.degree..
[0164] The inner seam does not lie in the preferred bending plane
of the fiber. In fiber 300, this is achieved by locating inner seam
321 away from the minor axis. Locating the inner seam away from the
preferred bending plane can be advantageous since it is believed
that losses (e.g., due to scattering and/or absorption) of guided
radiation is higher at the seam compared to other portions of the
confinement region. Further, it is believed that the energy density
of guided radiation in the core is higher towards the outside of a
bend in the fiber relative to the energy density at other parts of
the core. By locating the inner seam relative to the minor axis so
that the seam is unlikely to lie in the preferred bending plane
(e.g., where .alpha. is about 90.degree.), the probability that the
inner seam will lie towards the outside of a fiber bend is reduced.
Accordingly, the compounding effect of having a relatively high
loss portion of the confinement region at the region where the
energy density of guided radiation is high can be avoided, reducing
the loss associated with bends in the fiber.
[0165] Although inner seam 321 and outer seam 322 are positioned at
the same azimuthal position with respect to axis 399 in fiber 300,
in other embodiments the inner and outer seams can be located along
at different relative azimuthal positions with respect to the
fiber's axis.
[0166] As discussed previously, the cladding provides mechanical
support for the fiber's confinement region. Accordingly, the
thickness of cladding 360 can vary as desired along major axis 361.
The thickness of cladding 360 along minor axis 362 can also vary
but is generally less than the thickness along the major axis. In
some embodiments, cladding 360 is substantially thicker along the
major axis than confinement region 310.
[0167] For example, cladding 360 can be about 10 or more times
thicker than confinement region 310 (e.g., more than about 20, more
than about 30, more than about 50 times thicker) along the major
axis.
[0168] Fiber asymmetry can be introduced by shaving the perform,
and then drawing the fiber from the perform that has an asymmetric
cross-section. Alternatively, in some embodiments, the fiber
asymmetry can be introduced after the fiber is drawn from a
perform. For example, a fiber can be shaved or ground as part of
the production process after being drawn but before being
spooled.
[0169] Although fiber 300 includes a confinement region that has a
seam, in general, embodiments of asymmetric fibers can include
confinement regions with no seams (e.g., confinement regions that
are formed from a number of annular layers).
[0170] Furthermore, while fiber 300 has a shape composed of two
circular arcs and two straight lines, in general, fibers can have
other shapes. For example, fibers can have asymmetric polygonal
shapes, can be formed from arcuate portions having different radii
of curvature, and/or from arcuate portions that curve in opposite
directions. Generally, the shape should provide the fiber with a
preferred bending plane.
[0171] While the foregoing fibers are asymmetric with respect to
their cross-sectional shape, in general, fibers can be asymmetric
in a variety of ways in order to provide a preferred bend plane.
For example, in some embodiments, fibers can include material
asymmetries that give rise to a preferred bend plane. Material
asymmetries refer to variations between the material properties of
different portions of a fiber that cause the fiber to bend
preferably in a particular way. For example, a portion of a fiber
cladding can be formed from a material that is mechanically less
rigid that other portions, causing the fiber to bend preferably at
that portion. Mechanical variations can be caused by compositional
changes or by physical differences in portions having the same
composition. Compositional differences can be introduced, e.g., by
doping portions of a fiber or fiber preform with a dopant that
alters the mechanical properties of a fiber. As another example,
compositional differences can be introduced by forming different
portions of a fiber from different compounds. Physical differences
refer to, e.g., differences in the degree of crystallinity in
different portions of a fiber. Physical differences, such as
differences in crystallinity, can be introduced by selectively
heating and/or cooling portions of a fiber during fiber
fabrication, and/or using different rates of heating/cooling on
different fiber portions.
[0172] Furthermore, in some embodiments, fibers can include a
symmetric first cladding, but can include additional structure
outside of the cladding that cause the fiber to bend preferably in
a particular plane. For example, fibers can be placed in one or
more sheaths that are asymmetric when it comes to allowing the
fiber to bend.
[0173] Referring again to FIG. 1, laser system 100 also includes a
cooling apparatus 170, which delivers a cooling fluid (e.g., a gas
or a liquid) to fiber 120 via a delivery tube 171 and coupling
assembly 130. The cooling fluid is pumped through the core and
absorbs heat from the fiber surface adjacent the core. In the
present embodiment, the cooling fluid flows in the same direction
as the radiation from laser 110, however, in some embodiments, the
cooling fluid can be pumped counter to the direction of propagation
of the laser radiation.
[0174] The flow rate of the cooling fluid through the core of
photonic crystal fiber 120 can vary as desired. Typically, the flow
rate depends on the operating power of the laser, the absorption of
the fiber at the operating wavelength, the length of the fiber, and
the size of the fiber core, for example. Generally, the flow rate
should be sufficient to cool the fiber at its operating power. In
some embodiments, the flow rate can be about 0.1 liters/min or more
(e.g., about 0.5 liters/min or more, about 1 liter/min or more,
about 2 liters/min or more, about 5 liters/min or more, about 8
liters/min or more, about 9 liters/min or more, about 10 liters/min
or more).
[0175] The pressure of cooling fluid exhausted from the fiber can
vary. In some embodiments, the pressure of the cooling fluid can be
relatively high. For example, where the fluid exits from the same
end of the fiber as the radiation, a cooling gas can be at
sufficiently high pressure to clear debris from the target tissue
of the patient. The gas pressure can be about 0.2 PSI or more
(e.g., about 0.5 PSI or more, about 1 PSI or more). In some
embodiments, the pressure of a gas exiting the core of a fiber can
correspond to a flow rate of about 1 liter/min or more (e.g., about
2 liter/min or more, about 5 liter/min or more, about 8 liter/min
or more, about 10 liter/min or more) through a 1 meter length of
fiber having a core diameter of about 500 .mu.m.
[0176] The flow rate can be nominally constant while the system is
activated, or can vary depending on the state operation of the
laser system. For example, in some embodiments, the flow rate can
be adjusted based on whether radiation is being directed through
fiber 120 or not. At times where the laser is activated and
radiation is directed through the fiber, the flow rate can be at a
level sufficient to adequately cool the fiber.
[0177] However, between radiation doses, the system can reduce the
flow rate to a lower level (e.g., about 10% or less than the rate
used to cool the fiber while the laser is activated). The gas flow
rate can be triggered using remote control 152 or an additional
remote control that the operator can easily operate while using the
system.
[0178] In general, the temperature of the cooling fluid directed to
the fiber can vary. In some embodiments, the cooling fluid is
directed to the fiber at ambient temperature (e.g., at room
temperature). In certain embodiments, the cooling fluid is cooled
below ambient temperature prior to cooling the fiber. The cooling
fluid can be cooled so that fluid exhausted from the fiber is
within a certain temperature range. For example, the cooling fluid
can be sufficiently cooled so that fluid exhausted from the fiber
does not scald the patient if it comes into contact with the
patient. As another example, the cooling fluid can be sufficiently
cooled so that fluid exhausted from the fiber is between room
temperature and body temperature. In some embodiments, the cooling
fluid directed to the fiber can be cooled so that it has a
temperature below room temperature. For example, the fluid can have
a temperature of about 20.degree. C. or less (e.g., about
10.degree. C. or less, about 0.degree. C or less, about -10.degree.
C. or less, about -20.degree. C. or less, about -50.degree. C. or
less).
[0179] In certain embodiments, where the cooling fluid flows
through the fiber core in the laser radiation propagation
direction, it can perform additional functions where it impinges on
the target tissue of the patient. For example, in some embodiments,
heated fluid (e.g., gas) exiting the fiber can reduce bleeding at
incised blood vessels (or other tissue) by enhancing coagulation of
the blood. It is believed that coagulation of blood is accelerated
at temperatures of about 60.degree. C. or more. Accordingly, where
the gas exiting the fiber impinging the target tissue is about
60.degree. C. or more, it can increase the rate at which blood
coagulates, which can assist the surgeon by reducing the need to
suction blood from the operating area. In some embodiments, the
temperature of gas exiting the fiber can be, for example, about
50.degree. C. or more, about 60.degree. C. or more, about
65.degree. C. or more, about 70.degree. C. or more, about
80.degree. C. or more, about 90.degree. C. or more, about
100.degree. C. or more). Alternatively, in certain embodiments, the
temperature of the gas exiting the fiber can be below room
temperature (e.g., about 10.degree. C. or less, about 0.degree. C.
or less). For example, the system can provide cooled gas to the
target location in procedures where it is beneficial to cool tissue
before irradiating the tissue. In certain embodiments, the
temperature of gas exiting the fiber can be approximately at body
temperature (e.g., at about 37.degree. C.),
[0180] Gas flowing through the fiber core can be heated by about
5-10.RTM. C./Watt of input power (e.g., about 7-8.degree. C./Watt).
For example, a fiber having an input power of about 20 Watts could
heat gas flowing through its core by about 100-200.degree. C.
[0181] In some embodiments, the fluid flowing through the fiber's
core can be used to deliver other substances to the target tissue.
For example, atomized pharmaceutical compounds could be introduced
into a gas that is flowed through the core and delivered via the
photonic crystal fiber to the target tissue.
[0182] In general, the type of cooling fluid can vary as desired.
The cooling fluid can be liquid, gas, or superfluid. In some
embodiments, the cooling fluid includes a noble gas (e.g., helium,
neon, argon, krypton, and/or xenon), oxygen, carbon dioxide, and/or
nitrogen. The cooling fluid can be composed substantially of a
single compound (e.g., having a purity of about 98% or more, about
99% or more, about 99.5% or more, about 99.8% or more, about 99.9%
or more), or can be a mixture (e.g., air or heliox).
[0183] In some embodiments, the cooling fluid is selected based on
its ability to cool the fiber. The cooling ability of a fluid can
depend on the fluids flow rate and/or the fluids thermal
conductivity. Helium gas, for example, has a relatively high
thermal conductivity compared to other gases. Furthermore, for a
given pressure drop, helium can have a higher flow rate than other
gases, such as nitrogen. Accordingly, in some embodiments, helium
can be selected based on its ability to cool the fiber better than
other gases.
[0184] Alternatively, or additionally, the cooling fluid can be
selected based on whether or not it has any adverse interactions
with the patient. For example, in embodiments where the cooling
fluid is in close proximity to the patient, it can be selected
based on its relatively low toxicity. In certain embodiments, a
cooling fluid can be selected based on its solubility compared to
other fluids. A fluid with relatively low solubility in blood can
reduce the risk of the patient having an embolism due to exposure
to the cooling fluid. An example of a fluid with relatively low
toxicity and relatively low solubility is helium gas.
[0185] The cooling fluid can also be selected based on other
criteria, such as its reactivity with other elements (e.g.,
flammability). In some embodiments, a cooling fluid, such as
helium, can be selected based on its inert characteristics (e.g.,
inflammability).
[0186] In certain embodiments, a protective sleeve can be attached
to the output end of photonic crystal fiber 120. Sleeves can be
used to prevent debris buildup and clogging of the fiber's output
end. An example of a sleeve 401 is shown in FIG. 4A. Sleeve 401 is
attached to the output end of a photonic crystal fiber 410. Sleeve
401 includes a collar 425 that maintains a stand off distance 405
between the output end of the fiber and a distal opening 430 of the
sleeve. Typically, stand off distance 405 is from about 0.5 cm to
about 4 cm long. Radiation 411 exiting core 420 of fiber 410 exits
the sleeve through distal opening 430.
[0187] Sleeve 401 can also include perforations to reduce the
pressure of fluid exiting the fiber at distal opening 430. For
example, sleeve 401 includes secondary openings 435 and 436 that,
along with distal opening 430, provide paths through which fluid
exiting core 420 can exit the sleeve.
[0188] Typically, sleeves are formed from rigid materials that can
be readily sterilized. For example, sleeves can be formed from
stainless steel. Sleeves can be disposable or reusable.
[0189] Another example of a sleeve is sleeve 401A shown in FIG. 4B.
Sleeve 401A narrows along its length, having a larger diameter 402B
where it attaches to the output end of fiber 401 compared to the
diameter 402A near the distal opening. The narrowing sleeve
increases the pressure of fluid from core 420 in the sleeve,
increasing the fluid pressure at openings 435A and 435B, thereby
reducing the possibility of debris being sucked into the sleeve
through these openings.
[0190] In some embodiments, sleeves can include one or more optical
components. For example, referring to FIG. 4C, a sleeve 401B can
include a reflector 440 (e.g., a mirror) attached near the distal
opening. Reflector 440 redirects radiation 411 exiting core 420,
and can enable an operator to direct the radiation into confined
spaces not otherwise accessible.
[0191] In embodiments, sleeves can also include transmissive
optical components. For example, referring to FIG. 4D, a sleeve
401C includes a lens 450 mounted near distal opening 430. Lens is
mounted within the sleeve by a lens mount 451, which is positioned
between distal opening 430 and secondary openings 435 and 436 so
that fluid from the fiber can still exit sleeve 401C through
openings 435 and 436. Lens 450 focuses radiation 411 exiting core
420 to a waist at some position beyond distal opening 430. Another
example of a transmissive optical component that can be mounted
within a sleeve is a transmissive optical flats, which can serve as
a window for the transmission of radiation exiting the fiber core
while preventing fluid flow through distal opening 430.
[0192] As discussed previously, in laser system 100, light is
coupled from laser 110 and fluid from fluid source 170 into fiber
120 by coupling assembly 130. Referring to FIG. 5A, an example of a
coupler for coupling gas and radiation into a photonic crystal
fiber is coupling assembly 500. Coupling assembly 500 includes a
first portion 510 that receives radiation from the laser and gas
from a gas source, and a second portion 520 that connects to
photonic crystal fiber 120. First portion 510 is coupled to second
portion 520 by a flexible junction 505 (e.g., a metallic bellows or
rubber tube).
[0193] First portion 510 includes a lens holder 502 and an adaptor
504 for the lens holder. The lens holder can be a commercially
available lens holder. When coupled to lens holder 5-2, adaptor 504
secures a lens 501 in the lens holder. An o-ring 503 creates a seal
between adaptor 504 and lens 501. Adaptor 504 also includes a
fitting 504a for connecting to tube that supplies gas to the
system. In some embodiments, fitting 504a includes a barbed hose
fitting.
[0194] Portion 520 includes a connector alignment stage 508
including a fiber optic connector receptacle (e.g., a commercially
available stage, such as component LP-1A, available from Newport
(Irvine, Calif.)). Stage 508 is connected to flexible junction 505
by an adaptor 506. An o-ring 507 creates a seal between stage 508
and adaptor 506. A fiber optic connector 509 couples photonic
crystal fiber 510 to stage 58. Another o-ring 511 creates a seal
between fiber optic connector 509 and stage 508.
[0195] Another example of a coupling assembly is shown in FIG. 5B.
Coupling assembly 530 includes a laser connector 540 that attaches
to the output terminal 111 of laser 110. Coupling assembly 530
includes a housing 531 attached to laser connector 540. The housing
includes a fluid inlet port 533 and a radiation output port 534. A
fiber optic connector 550 affixes to radiation output port 534,
positioning an end of a photonic crystal fiber 551 relative to the
radiation output port. In addition, a connector 560 connects a
fluid conduit 561 to the housing by attaching to fluid input port
533.
[0196] A retardation reflector 532 is positioned within housing
531. Retardation reflector 532 directs linearly polarized radiation
541 entering the housing from the laser towards a radiation output
terminal 534, modifying the polarization state so that reflected
radiation 542 is circularly polarized. More generally, the
reflective retarder modifies the polarization state of the laser
radiation to provide a lower loss polarization to fiber 551. In
embodiments, average losses of circularly polarized radiation may
be lower than linearly polarized radiation where the fiber has high
loss regions that may be coincident with the plane of polarization.
For example, photonic crystal fibers that have a confinement region
having a seam can exhibit higher losses for radiation polarized in
the plane of the seam compared to circularly polarized light.
Alternatively, or additionally to having a retarder, fiber 551 can
be attached with its seam (or other high loss region) in a
particular orientation with respect to the polarization state of
radiation from the laser.
[0197] Examples of a reflective retarder suitable for 10.6 micron
radiation are series PRR: Silicon & Copper Phase Retardation
Reflectors (commercially-available from Laser Research Optics
(Providence, R.I.). Transmissive retarders (e.g., formed from
birefringent crystals) can be used in place of, or in addition to,
retardation reflector 532.
[0198] Coupling assembly 530 also includes a lens 545, mounted
within housing 531 by mount 535, which focuses reflected radiation
542 to a waist at radiation output port 534 where it couples into
the core of fiber 551. Lenses suitable for use at 10.6 micron
wavelengths, for example, can be formed from ZnSe.
[0199] In embodiments where cooling fluid is not coupled into the
fiber's core, other coupling assemblies can be used. Generally, in
such embodiments, any coupler suitable for the wavelength and
intensity at which the laser system operates can be used. One is
type of a coupler is described by R. Nubling and J. Harrington in
"Hollow-waveguide delivery systems for high-power, industrial
CO.sub.2 lasers," Applied Optics, 34, No. 3, pp. 372-380 (1996).
Other examples of couplers include one or more focusing elements,
such as one or more lenses. More generally, the coupler can include
additional optical components, such as beam shaping optics, beam
filters and the like.
[0200] In general, coupling efficiency can be relatively high. For
example, coupling assembly 130 can couple more than about 70% of
the laser output at the guided wavelength into a guided mode in the
fiber (e.g., about 80% or more, 90% or more, 95% or more, 98% or
more). Coupling efficiency refers to the ratio of power guided away
by the desired mode to the total power incident on the fiber.
[0201] While laser system 100 includes handpiece 140, systems can
include different types of handpieces depending on the medical
application for which they are being used. In general, a handpiece
includes a portion that the operator can grip, e.g., in his/her
palm or fingertips, and can include other components as well. In
certain embodiments, handpieces can include endoscopes (e.g.,
flexible or rigid endoscopes), such as a cystoscopes (for
investigating a patient's bladder), nephroscopes (for investigating
a patient's kidney), bronchoscopes (for investigating a patient's
bronchi), laryngoscopes (for investigating a patient's larynx),
otoscopes (for investigating a patient's ear), arthroscopes (for
investigating a patient's joint), laparoscopes (for investigating a
patient's abdomen), and gastrointestinal endoscopes. Another
example of a handpiece is a catheter, which allows an operator to
position the output end of the photonic crystal fiber into canals,
vessels, passageways, and/or body cavities.
[0202] Moreover, handpieces can be used in conjunction with other
components, without the other component being integrated into the
handpiece. For example, handpieces can be used in conjunction with
a trocar to position the output end of a photonic crystal fiber
within an abdominal cavity of a patient. In another example, a
handpiece can be used in conjunction with a rigid endoscope, where
the rigid endoscope is not attached to the gripping portion of the
handpiece or to the photonic crystal fiber.
[0203] Referring to FIG. 6, in some embodiments, a handpiece 680
includes a narrow conduit 684 that includes a channel through which
photonic crystal fiber 120 is inserted. Conduit 684 can be made
from a rigid, but deformable, material (e.g., stainless steel).
This allows the operator to bend the conduit (e.g., by hand or
using a tool) to a desired amount (e.g., such as at bend 686) for a
procedure, where the conduit retains the bend until the operator
straightens it or bends it in a different way. Handpiece 680 also
includes a gripping portion 682 attached to conduit 684, which
allows the operator to comfortably hold the handpiece.
[0204] In certain embodiments, handpieces can include actuators
that allow the operator to bend the fiber remotely, e.g., during
operation of the system. For example, referring to FIG. 7A, in some
embodiments, laser radiation 112 can be delivered to target tissue
699 within a patient 601 using an endoscope 610. Endoscope 610
includes a gripping portion 611 and a flexible conduit 615
connected to each other by an endoscope body 616. An imaging cable
622 housing a bundle of optical fibers is threaded through a
channel in gripping portion 611 and flexible conduit 615. Imaging
cable 622 provide illumination to target tissue 699 via flexible
conduit 615. The imaging cable also guides light reflected from the
target tissue to a controller 620, where it is imaged and displayed
providing visual information to the operator. Alternatively, or
additionally, the endoscope can include an eyepiece lens that
allows the operator to view the target area directly through the
imaging cable.
[0205] Endoscope 610 also includes an actuator 640 that allows the
operator to bend or straighten flexible conduit 615. In some
embodiments, actuator 640 allows flexible conduit 615 to bend in
one plane only. Alternatively, in certain embodiments, the actuator
allow the flexible conduit to bend in more than one plane.
[0206] Endoscope 610 further includes an auxiliary conduit 630
(e.g., a detachable conduit) that includes a channel through which
fiber 120 is threaded. The channel connects to a second channel in
flexible conduit 615, allowing fiber 120 to be threaded through the
auxiliary conduit into flexible conduit 615. Fiber 120 is attached
to auxiliary conduit in a matter than maintains the orientation of
the fiber with respect the channel through flexible conduit 615,
thereby minimizing twisting of the photonic crystal fiber about its
waveguide axis within the flexible conduit. In embodiments where
photonic crystal fiber 120 has a confinement region that includes a
seam, the fiber can be attached to the auxiliary conduit so that
the seam is not coincident with a bend plane of the flexible
conduit.
[0207] In general, photonic crystal fibers can be used in
conjunction with commercially-available endoscopes, such as
endoscopes available from PENTAX Medical Company (Montvale, N.J.)
and Olympus Surgical & Industrial America, Inc. (Orangeburg,
N.Y.).
[0208] Auxiliary conduit 630 can be configured to allow the user to
extend and/or retract the output end of the photonic crystal fiber
within flexible conduit 615. For example, referring to FIG. 7B, in
some embodiments, auxiliary conduit 630 of endoscope 610 can
include two portions 631 and 632 that are moveable with respect to
each other. Portion 632 is attached to endoscope body 616, while
portion 631 telescopes with respect to portion 632. Portion 632
includes a connector 636 that connects to a fiber connector 638
attached to fiber 120. The mating mechanism of connector 636 and
fiber connector 638 can allow for quick and simple removal and
attachment of the photonic crystal fiber to the endoscope. When
attached, connector 636 and fiber connector 638 substantially
prevent fiber 120 from twisting, maintaining its orientation about
the fiber axis within flexible conduit 615. The connectors can
maintain the orientation of the fiber in the conduit with a seam in
the fiber oriented away from a bend plane of the conduit, for
example. Furthermore, when portion 631 extends or retracts with
respect to portion 632, it extends or retracts the output end 645
of fiber 120 with respect to the distal end 618 of flexible conduit
615. Auxiliary conduit 630 also includes a locking mechanism 634
(e.g., a latch or clamp) that allows the user to lock the portion
631 with respect to portion 632. The locking mechanism prevents
unwanted movement of fiber 120 within flexible conduit 615 while
radiation is being delivered to the patient.
[0209] While laser systems 100 and 600 include a single length of a
photonic crystal fiber that delivers radiation from laser 110 to
the target location, multiple connected lengths of photonic crystal
fiber can also be used. For example, referring to FIG. 7C, a laser
system 700 includes two lengths of photonic crystal fiber 720 and
721 rather than a single length of photonic crystal fiber as laser
systems 100 and 600. Photonic crystal fiber lengths 720 and 721 are
coupled together by a connector 730 that attaches to auxiliary
conduit 630 of endoscope 610.
[0210] Laser system 700 includes a secondary cooling apparatus 740
in addition, or alternatively, to cooling apparatus 170. Photonic
crystal fiber length 720 is placed within a sheath 744, which is
connected to secondary cooling apparatus 740 by a delivery tube
742. Secondary cooling apparatus 740 cools photonic crystal fiber
length 720 by pumping a cooling fluid through sheath 744.
[0211] Secondary cooling apparatus 740 can recirculate the cooling
fluid it pumps through sheath 744. For example, sheath 744 can
include an additional conduit that returns the cooling fluid to
secondary cooling apparatus 740. A heat exchanger provided with the
secondary cooling system can actively cool the exhausted cooling
fluid before the secondary cooling system pumps the fluid back to
sheath 744.
[0212] The cooling fluid can be the same or different as the
cooling fluid pumped into the core of the photonic crystal fiber by
cooling apparatus 170. In some embodiments, cooling apparatus 170
pumps a gas through the core of the fiber, while secondary cooling
apparatus 740 cools the fiber using a liquid (e.g., water).
[0213] Sheath 744 can perform a protective function, shielding
photonic crystal fiber length 720 from environmental hazards. In
some embodiments, sheath 744 includes a relatively rigid material
(e.g., so that sheath 744 is more rigid than photonic crystal fiber
length 720), reducing flexing of photonic crystal fiber length 720.
In some embodiments, sheath 744 is formed from a relatively rigid
material, such as nitinol (commercially-available from Memry, Inc.,
Bethel, Conn.).
[0214] In embodiments, using two lengths of photonic crystal fiber
can prolong the usable lifetime of at least one of the lengths. For
example, due to the additional cooling and/or protection afforded
the fiber length by cooling apparatus 740 and/or sheath 744,
photonic crystal fiber length 720 can be replaced less often than
fiber length 721. In some embodiments, fiber length 721 can be used
multiple times, while fiber length 721 is discarded after each
use.
[0215] While laser system 700 utilizes two connected lengths of
photonic crystal fiber, more generally, waveguides other than
photonic crystal waveguides can also be connected to a length of
photonic crystal fiber to provide a conduit for delivering
radiation from a laser to the target location. For example, a
length of a hollow metallic waveguide can be connected to a length
of a photonic crystal fiber to provide a conduit for IR
radiation.
[0216] Furthermore, in general, other conduits can be bundled with
photonic crystal fibers in a medical laser system to, e.g., deliver
something to, remove something from, or to observe the target
tissue during the procedure. For example, as discussed in reference
to FIG. 7A, the photonic crystal fiber can be bundled with other
optical waveguides, such as an imaging cable used to illuminate
and/or image the target tissue using an imaging system. In certain
embodiments, laser systems can deliver radiation from more than one
radiation source to the patient by delivering radiation from a
laser radiation through the photonic crystal fiber, and radiation
from a second source (e.g., a second laser) through the other
conduit (e.g., an optical fiber). As an example, referring to FIG.
8, in certain embodiments, a system 800 includes a fiber waveguide
830 and a photonic crystal fiber 810, with a portion of fiber
waveguide 830 and photonic crystal fiber 810 being bundled within a
jacket 850 (e.g., a flexible jacket, such as a flexible polymer
jacket). Photonic crystal fiber 810 is coupled to a laser 820,
which delivers radiation at wavelength .lamda..sub.1 through the
core 812 of photonic crystal fiber 810. Fiber waveguide 830 is
coupled to another radiation source 840, which delivers radiation
at a different wavelength, .lamda..sub.2, through the core 832 of
fiber waveguide 830. Photonic crystal fiber 810 and fiber waveguide
830 deliver radiation (indicated by reference numerals 822 and 842,
respectively) at wavelengths .lamda..sub.1 and .lamda..sub.2,
respectively, to a common location.
[0217] Fiber waveguide 830 can be, for example, an optical fiber or
a photonic crystal fiber. Radiation source 840 can be a laser or
other light source (e.g., a bulb or light emitting diode). As an
example, in some embodiments, radiation source 840 is a laser that
emits visible radiation (e.g., .lamda..sub.2 is within a range from
about 400 nm to about 800 nm, such as 633 nm), such as a HeNe laser
and fiber waveguide 830 is an optical fiber. The visible radiation
emitted from fiber 830 allows the operator to aim the output end of
the photonic crystal fiber to the appropriate tissue before
delivering laser radiation from laser 820. In another example, the
other radiation source 840 is an Nd:YAG laser, which can also be
used to deliver radiation to the patient for photocoagulation or
photoablation purposes.
[0218] Jacket 850 can have a sufficiently small outer diameter to
allow the jacket to be used in conjunction with a variety of
handpieces. For example, the jacket can have an outer diameter of
about 2 mm or less, allowing the jacket to be inserted into a
standard-size channel of an endoscope.
[0219] In some embodiments, the photonic crystal fiber can be
bundled with a tube for delivering gas to (e.g., hot gas for blood
coagulation) or vacuuming debris at the target location, as an
alternative or in addition to being bundled with a fiber
waveguide.
[0220] For example, referring to FIG. 9, a system 900 a photonic
crystal fiber 910 is bundled with a tube 930 for exhausting fluid
(e.g., cooling fluid) exiting the photonic crystal fiber's core 912
at the fiber's output end. The system shown in FIG. 9 includes a
laser 920 and a fluid source 926 that deliver radiation and fluid
to the photonic crystal fiber's core 912 via a coupling assembly
924. The system also includes a pump that draws fluid exiting core
912 through tube 930 away from the patient.
[0221] The output end of fiber 910 and input end of tube 930 are
coupled together by a cap 960, that fits over the ends of the fiber
and tube. Cap 960 includes a window 962 that is made from a
material substantially transparent to the wavelength of radiation
being delivered from laser 920. Cap 960 positions window 962 in the
path of radiation 922 exiting core 912, allowing the system to
deliver the radiation to the patient. Fluid exiting core 912,
however, is drawn through an exhaust port 964 into tube 942. Pump
940, connected to the opposite end of tube 930, draws the fluid 942
through the tube away from the patient.
[0222] A portion of tube 930 and photonic crystal fiber 910 are
bundled together within a jacket 950, providing a flexible duct
that can be threaded through a channel in a handpiece (e.g., a
handpiece including an endoscope).
[0223] System 900 can be used in procedures where it is undesirable
to exhaust fluid (e.g., cooling fluid) to the tissue being exposed
to radiation. For example, where the radiation is being delivered
internally, where the exhausted fluid is toxic, or is at an
undesirable temperature (e.g., sufficiently hot to burn the exposed
tissue), an exhaust tube can be included with the photonic crystal
fiber to prevent exposure of the tissue to the fluid.
[0224] In some cases, the handpiece in a medical laser system can
be replaced by a robot, which can be operated remotely. For
example, robot-performed surgery is under consideration in
applications where a surgeon cannot easily or rapidly reach a
patient (e.g., a wounded soldier on a battlefield).
[0225] Since photonic crystal fibers are used in medical
procedures, they should be sterilizable. For example, photonic
crystal fibers should be able to withstand sterilizing procedures,
such as autoclaving. Typically, lengths of photonic crystal fiber
are provided to the user pre-sterilized and sealed in a container
(e.g., vacuum sealed in a container that has sufficient barrier
properties to prevent contamination of the fiber length during
storage and shipping). For example, sterilized lengths of photonic
crystal fiber (e.g., about 0.5 meters to about 2.5 meters lengths)
can be provided sealed (e.g., vacuum sealed) in a plastic container
(e.g., including a barrier film layer).
[0226] In general, the laser systems described above can be used in
a number of different medical applications. Generally, the type of
laser, wavelength, fiber length, fiber outer diameter, and fiber
inner diameter, among other system parameters, will be selected
according to the application. Medical applications include
aesthetic medical procedures, surgical medical procedures,
ophthalmic procedures, veterinary procedures, and dental
procedures.
[0227] Aesthetic procedures include treatment for: hair removal;
pulsed light skin treatments for reducing fine wrinkle lines, sun
damage, age spots, freckles, some birthmarks, rosacea, irregular
pigmentation, broken capillaries, benign brown pigment and
pigmentation; skin resurfacing; leg veins; vascular lesions;
pigmented lesions; acne; psoriasis & vitiligo; and/or cosmetic
repigmentation.
[0228] Surgical procedures include procedures for gynecology,
laparoscopy, condylomas and lesions of the external genitalia,
and/or leukoplakia. Surgical applications can also include
ear/nose/throat (ENT) procedures, such as laser assisted uvula
palatoplasty (LAUP) (i.e., to stop snoring); procedures to remove
nasal obstruction; stapedotomy; tracheobronchial endoscopy; tonsil
ablation; and/or removal of benign laryngeal lesions. Surgical
applications can also include breast biopsy, cytoreduction for
metastatic disease, treatment of decubitus or statis ulcers,
hemorrhoidectomy, laparoscopic surgery, mastectomy, and/or
reduction mammoplasty. Surgical procedures can also include
procedures in the field of podiatry, such as treatment of neuromas,
periungual, subungual and plantar warts, porokeratoma ablation,
and/or radical nail excision. Other fields of surgery in which
lasers may be used include orthopedics, urology, gastroenterology,
and thoracic & pulmonary surgery.
[0229] Ophthalmic uses include treatment of glaucoma, age-related
macular degeneration (AMD), proliferative diabetic retinopathy,
retinopathy of prematurity, retinal tear and detachment, retinal
vein occlusion, and/or refractive surgery treatment to reduce or
eliminate refractive errors.
[0230] Veterinary uses include both small animal and large animal
procedures.
[0231] Examples of dental applications include hard tissue, soft
tissue, and endodontic procedures. Hard tissue dental procedures
include caries removal & cavity preparation and laser etching.
Soft tissue dental procedures include incision, excision &
vaporization, treatment of gummy smile, coagulation (hemostasis),
exposure of unerupted teeth, aphthous ulcers, gingivoplasty,
gingivectomy, gingival troughing for crown impressions, implant
exposure, frenectomy, flap surgery, fibroma removal, operculectomy,
incision & drainage of abscesses, oral papilectomy, reduction
of gingival hypertrophy, pre-prosthetic surgery, pericoronitis,
peri implantitis, oral lesions, and sulcular debridement.
Endodontic procedures include pulpotomy, root canal debridement,
and cleaning. Dental procedures also include tooth whitening.
[0232] Generally, the type of laser, wavelength, fiber length,
fiber outer diameter, and fiber inner diameter, among other system
parameters, are selected according to the application. For example,
embodiments in which the laser is a CO.sub.2 laser, the laser
system can be used for surgical procedures requiring the ablation,
vaporization, excision, incision, and coagulation of soft tissue.
CO.sub.2 laser systems can be used for surgical applications in a
variety of medical specialties including aesthetic specialties
(e.g., dermatology and/or plastic surgery), podiatry,
otolaryngology (e.g., ENT), gynecology (including laparoscopy),
neurosurgery, orthopedics (e.g., soft tissue orthopedics),
arthroscopy (e.g., knee arthroscopy), general and thoracic surgery
(including open surgery and endoscopic surgery), dental and oral
surgery, ophthalmology, genitourinary surgery, and veterinary
surgery.
[0233] In some embodiments, CO.sub.2 laser systems can be used in
the ablation, vaporization, excision, incision, and/or coagulation
of tissue (e.g., soft tissue) in dermatology and/or plastic surgery
in the performance of laser skin resurfacing, laser derm-abrasion,
and/or laser burn debridement. Laser skin resurfacing (e.g,. by
ablation and/or vaporization) can be performed, for example, in the
treatment of wrinkles, rhytids, and/or furrows (including fine
lines and texture irregularities). Laser skin resurfacing can be
performed for the reduction, removal, and/or treatment of:
keratoses (including actinic keratosis), seborrhoecae vulgares,
seborrheic wart, and/or verruca seborrheica; vermillionectomy of
the lip; cutaneous horns; solar/actinic elastosis; cheilitis
(including actinic cheilitis); lentigines (including lentigo
maligna or Hutchinson's malignant freckle); uneven
pigmentation/dyschromia; acne scars; surgical scars; keloids
(including acne keloidalis nuchae); hemangiomas (including Buccal,
port wine and/or pyogenic granulomas/granuloma pyogenicum/granuloma
telagiectaticum); tattoos; telangiectasia; removal of skin tumors
(including periungual and/or subungual fibromas); superficial
pigmented lesions; adenosebaceous hypertrophy and/or sebaceous
hyperplasia; rhinophyma reduction; cutaneous papilloma; milia;
debridement of eczematous and/or infected skin; basal and squamous
cel carcinoma (including keratoacanthomas, Bowen's disease, and/or
Bowenoid Papulosis lesions); nevi (including spider, epidermal,
and/or protruding); neurofibromas; laser de-epithelialization;
tricoepitheliomas; xanthelasma palpebrarum; and/or syringoma.
CO.sub.2 laser systems can be used for laser ablation, vaporization
and/or excision for complete and/or partial nail matrixectomy, for
vaporization and/or coagulation of skin lesions (e.g., benign
and/or malignant, vascular and/or avascular), and/or for Moh's
surgery, for lipectomy. Further examples include using laser system
1300 for laser incision and/or excision of soft tissue for the
performance of upper and/or lower eyelid blepharoplasty, and/or for
the creation of recipient sites for hair transplantation.
[0234] In certain embodiments, CO.sub.2 laser systems is used in
the laser ablation, vaporization, and/or excision of soft tissue
during podiatry procedures for the reduction, removal, and/or
treatment of: verrucae vulgares/plantar warts (including
paronychial, periungual, and subungual warts); porokeratoma
ablation; ingrown nail treatment; neuromas/fibromas (including
Morton's neuroma); debridement of ulcers; and/or other soft tissue
lesions. CO.sub.2 laser systems can also be used for the laser
ablation, vaporization, and/or excision in podiatry for complete
and/or partial matrixectomy.
[0235] CO.sub.2 laser systems can be used for laser incision,
excision, ablation, and/or vaporization of soft tissue in
otolaryngology for treatment of: choanal atresia; leukoplakia
(including oral, larynx, uvula, palatal, upper lateral pharyngeal
tissue); nasal obstruction; adult and/or juvenile papillomatosis
polyps; polypectomy of nose and/or nasal passages; lymphangioma
removal; removal of vocal cord/fold nodules, polyps and cysts;
removal of recurrent papillomas in the oral cavity, nasal cavity,
larynx, pharynx and trachea (including the uvula, palatal, upper
lateral pharyngeal tissue, tongue and vocal cords); laser/tumor
surgery in the larynx, pharynx, nasal, ear and oral structures and
tissue; Zenker' diverticulum/pharynoesophageal diverticulum (e.g.,
endoscopic laser-assisted esophagodiverticulostomy); stenosis
(including subglottic stenosis); tonsillectomy (including tonsillar
cryptolysis, neoplasma) and tonsil ablation/tonsillotomy; pulmonary
bronchial and tracheal lesion removal; benign and malignant
nodules, tumors and fibromas (e.g., of the larynx, pharynx,
trachea, tracheobronchial/endobronchial); benign and/or malignant
lesions and/or fibromas (e.g., of the nose or nasal passages);
benign and/or malignant tumors and/or fibromas (e.g., oral);
stapedotomy/stapedectomy; acoustic neuroma in the ear; superficial
lesions of the ear (including chondrodermatitis nondularis chronica
helices/Winkler's disease); telangiectasia/hemangioma of larynx,
pharynx, and/or trachea (including uvula, palatal, and/or upper
lateral pharyngeal tissue); cordectomy, cordotomy (e.g., for the
treatment of vocal cord paralysis/vocal fold motion impairment),
and/or cordal lesions of larynx, pharynx, and/or trachea;
myringotomy/tympanostomy (e.g., tympanic membrane fenestration);
uvulopalatoplasty (e.g., LAUP); turbinectomy and/or turbinate
reduction/ablation; septal spur ablation/reduction and/or
septoplasty; partial glossectomy; tumor resection on oral,
subfacial and/or neck tissues; rhinophyma; verrucae vulgares;
and/or gingivoplasty/gingivectomy.
[0236] In some embodiments, CO.sub.2 laser systems can be used for
the laser incision, excision, ablation, and/or vaporization of soft
tissue in gynecology for treatment of: conizaton of the cervix
(including cervical intraepithelial neoplasia, vulvar and/or
vaginal intraepithelial neoplasia); condyloma acuminata (including
cervical, genital, vulvar, preineal, and/or Bowen's disease, and/or
Bowenoid papulosa lesions); leukoplakia (e.g., vulvar dystrophies);
incision and drainage of Bartholin's and/or nubuthian cysts; herpes
vaporization; urethral caruncle vaporization; cervical dysplasia;
benign and/or malignant tumors; and/or hemangiomas.
[0237] CO.sub.2 laser systems can be used for the vaporization,
incision, excision, ablation and/or coagulation of soft tissue in
endoscopic and/or laparoscopic surgery, including gynecology
laparoscopy, for treatment of: endometrial lesions (inclusing
ablation of endometriosis); excision/lysis of adhesions;
salpingostomy; oophorectomy/ovariectomy; fimbroplasty; metroplasty;
tubal microsurgery; uterine myomas and/or fibroids; ovarian
fibromas and/or follicle cysts; uterosacral ligament ablation;
and/or hysterectomy.
[0238] In certain embodiments, CO2 laser systems are used for the
laser incision, excision, ablation, and/or vaporization of soft
tissue in neurosurgery for the treatment of cranial conditions,
including: posterior fossa tumors; peripheral neurectomy; benign
and/or malignant tumors and/or cysts (e.g., gliomos, menigiomas,
acoustic neuromas, lipomas, and/or large tumors); arteriovenous
malformation; and/or pituitary gland tumors. In some embodiments,
CO.sub.2 laser systems are used for the laser incision, excision,
ablation, and/or vaporization of soft tissue in neurosurgery for
the treatment of spinal cord conditions, including:
incision/excision and/or vaporization of benign and/or malignant
tumors and/or cysts; intra- and/or extradural lesions; and/or
laminectomy/laminotomy/microdisectomy.
[0239] CO.sub.2 laser systems can be used for the incision,
excision, and/or vaporization of soft tissue in orthopedic surgery
in applications that include arthroscopic and/or general surgery.
Arthroscopic applications include: menisectomy; chondromalacia;
chondroplasty; ligament release (e.g., lateral ligament release);
excision of plica; and/or partial synovectomy. General surgery
applications include: debridement of traumatic wounds; debridement
of decubitis and/or diabetic ulcers; microsurgery; artificial joint
revision; and/or polymer (e.g., polymethylmethacrylate)
removal.
[0240] CO.sub.2 laser systems can also be used for incision,
excision, and/or vaporization of soft tissue in general and/or
thoracic surgery, including endoscopic and/or open procedures. Such
applications include: debridement of decubitus ulcers, stasis,
diabetic and other ulcers; mastectomy; debridement of burns; rectal
and/or anal hemorrhoidectomy; breast biopsy; reduction mammoplasty;
cytoreduction for metastatic disease; laparotomy and/or
laparoscopic applications; mediastinal and/or thoracic lesions
and/or abnormalities; skin tag vaporization; atheroma; cysts
(including sebaceous cysts, pilar cysts, and/or mucous cysts of the
lips); pilonidal cyst removal and/or repair; abscesses; and/or
other soft tissue applications.
[0241] In certain embodiments, CO.sub.2 laser systems can be used
for the incision, excision, and/or vaporization of soft tissue in
dentistry and/or oral surgery, including for: gingivectomy;
gingivoplasty; incisional and/or excisional biopsy; treatment of
ulcerous lesions (including aphthous ulcers); incision of infection
when used with antibiotic therapy; frenectomy; excision and/or
ablation of benign and/or malignant lesions;
homeostasis;operculectomy; crown lengthening; removal of soft
tissue, cysts, and/or tumors; oral cavity tumors and/or
hemangiomas; abscesses; extraction site hemostasis; salivary gland
pathologies; preprosthetic gum preparation; leukoplakia; partial
glossectomy; and/or periodontal gum resection.
[0242] In some embodiments, CO.sub.2 laser systems can be used for
incision, excision, and/or vaporization of soft tissue in
genitourinary procedures, including for: benign and/or malignant
lesions of external genitalia; condyloma; phimosis; and/or
erythroplasia.
EXAMPLE
[0243] Surgery was performed to remove portions of the larynx from
a dog using a CO.sub.2 laser system operating at 10.6 microns. The
photonic crystal fiber used in this procedure had a hollow core
approximately 550 microns in diameter. The fiber had spiral
confinement region that included a radial profile of approximately
20 PES/As.sub.2Se.sub.3 bilayers. The bilayer thickness was
approximately 3 microns, with a thickness ration of approximately 2
to 1 (PES to As.sub.2Se.sub.3). The fiber's cladding was formed
from PES, and the fiber's OD was approximately 1500 microns. The
fiber was 1.5 m long.
[0244] A complete en bloc supraglottic laryngectomy was performed
including a cordectomy. The laser radiation was delivered using the
photonic crystal fiber with a semi-rigid hand-piece. The hand-piece
was inserted through a rigid laryngoscope. The input power into the
fiber was approximately 20 Watts. The radiation power exiting the
fiber was approximately 7 Watts. Nitrogen was blown through the
fiber in the same direction as the radiation. The nitrogen flow
rate was approximately 1 liter/min.
[0245] Radiation was delivered to the target tissue with a few
millimeters (e.g., about 5 mm-1 cm) standoff between the distal end
of the fiber and the target tissue. The supraglottis was removed
with just one pause to cauterize any incised blood vessels or to
suction any blood away from the target area. Minimal bleeding was
observed, with blood from incised vessels coagulating as it was
exposed to the output from the fiber. The procedure lasted about 45
minutes, during which time the supraglottis and left cord were
removed from the dog.
Additional Embodiments
[0246] A number of embodiments of the invention have been
described. Nevertheless, it will be understood that various
modifications may be made without departing from the spirit and
scope of the invention. Accordingly, other embodiments are within
the scope of the following claims.
* * * * *
References