U.S. patent application number 11/901785 was filed with the patent office on 2008-03-13 for high-efficiency, side-pumped diode laser system.
This patent application is currently assigned to BIOLASE Technology, Inc.. Invention is credited to Manvel Artyom Andriasyan.
Application Number | 20080065057 11/901785 |
Document ID | / |
Family ID | 38623276 |
Filed Date | 2008-03-13 |
United States Patent
Application |
20080065057 |
Kind Code |
A1 |
Andriasyan; Manvel Artyom |
March 13, 2008 |
High-efficiency, side-pumped diode laser system
Abstract
An apparatus for cutting or ablating hard tissue, includes an
optical cavity; a gain medium disposed within the optical cavity; a
diode light pump disposed within the optical cavity and optically
aligned to light pump the gain medium to generate laser light. The
generated laser light has a wavelength and power density suitable
for cutting and ablating hard tissue.
Inventors: |
Andriasyan; Manvel Artyom;
(San Diego, CA) |
Correspondence
Address: |
STOUT, UXA, BUYAN & MULLINS LLP
4 VENTURE, SUITE 300
IRVINE
CA
92618
US
|
Assignee: |
BIOLASE Technology, Inc.
|
Family ID: |
38623276 |
Appl. No.: |
11/901785 |
Filed: |
September 18, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10178080 |
Jun 21, 2002 |
7288086 |
|
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11901785 |
Sep 18, 2007 |
|
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60299944 |
Jun 21, 2001 |
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Current U.S.
Class: |
606/10 |
Current CPC
Class: |
A61B 18/20 20130101 |
Class at
Publication: |
606/010 |
International
Class: |
A61B 18/20 20060101
A61B018/20 |
Claims
1. A method of cutting or ablating hard tissue, comprising the
following steps: activating a diode array to side pump a gain
medium and generate at least one pulse of electromagnetic energy
having a full-width half-max range closer to a beginning than an
end of the pulse; placing fluid into a volume in close proximity to
the hard tissue; and directing pulses of the electromagnetic energy
into the volume in close proximity to the hard tissue to effectuate
the cutting or ablating of the hard tissue.
2. The method as set forth in claim 1, wherein: the gain medium
comprises a laser rod; the electromagnetic energy comprises laser
light; and the laser light has a wavelength, pulse format, and
power density suitable for cutting and ablating hard tissue and
further has a wavelength which is highly absorbed by water.
3. The method as set forth in claim 1, wherein the gain medium
comprises an Erbium-based laser rod.
4. The method as set forth in claim 1, wherein the electromagnetic
energy is generated in the TEMoo mode to attenuate thermal
effects.
5. The method as set forth in claim 1, wherein the hard tissue
comprises tooth tissue.
6. The method as set forth in claim 1, wherein the hard tissue
comprises bone.
7. The method as set forth in claim 1, wherein temporal pulse
control is used to attain a uniform temporal pulse pattern.
8. The method as set forth in claim 7, wherein gain switching or
Q-switching is used in attaining the uniform temporal pulse
pattern.
9. A method of cutting or ablating hard tissue, comprising the
following steps: activating a diode light pump to light pump a gain
medium and generate at least one pulse of electromagnetic energy
having a full-width half-max value in a range from about 0.025 to
about 250 microseconds; placing fluid into a volume in close
proximity to the hard tissue; and directing pulses of the
electromagnetic energy into the volume in close proximity to the
hard tissue to generate the cutting or ablating of the hard
tissue.
10. The method as set forth in claim 9, wherein: the gain medium
comprises a laser rod; the electromagnetic energy comprises laser
light; and the laser light has a pulse format and a wavelength
which are suitable for cutting and ablating hard tissue and which
are highly absorbed by water.
11. The method as set forth in claim 9, wherein the gain medium
comprises an Erbium-based laser rod.
12. The method as set forth in claim 9, wherein the electromagnetic
energy is generated in the TEMoo mode to attenuate thermal
effects.
13. The method as set forth in claim 9, wherein the hard tissue
comprises tooth tissue.
14. The method as set forth in claim 9, wherein the hard tissue
comprises bone.
15. The method as set forth in claim 9, wherein temporal pulse
control is used to attain a uniform temporal pulse pattern.
16. The method as set forth in claim 15, wherein gain switching or
Q-switching is used in attaining the uniform temporal pulse
pattern.
17. The method as set forth in claim 9, wherein the diode light
pump comprises a diode array.
18. The method as set forth in claim 9, wherein the diode light
pump comprises a diode array, which is placed within an optical
cavity so that the diode array is optically aligned to side pump
the gain medium.
19. An apparatus for cutting or ablating hard tissue comprising a
diode light pump disposed within an optical cavity and optically
aligned to light pump a gain medium within the optical cavity to
generate at least one pulse of electromagnetic energy having a
full-width half-max range closer to a beginning than an end of the
pulse the apparatus being configured to direct the electromagnetic
energy into a volume in close proximity to the hard tissue so that
the hard tissue is cut or ablated, wherein the electromagnetic
energy is generated in the TEMoo mode to attenuate thermal
effects.
20. The apparatus as set forth in claim 19, wherein: the gain
medium comprises a laser rod; the electromagnetic energy comprises
laser light; the laser light has a wavelength, pulse, and power
density suitable for cutting and ablating hard tissue and further
has a wavelength that is highly absorbed by water; and the
apparatus further comprises a fluid output configured to place
fluid into a volume in close proximity to the hard tissue, whereby
the laser light is highly absorbed by fluid in the volume.
21. The apparatus as set forth in claim 19, wherein: the gain
medium comprises an Erbium-based laser rod; the electromagnetic
energy comprises laser light having a wavelength, pulse, and power
density suitable for cutting and ablating hard tissue; and the
apparatus further comprises a fluid output configured to place
fluid into a volume in close proximity to the hard tissue, whereby
the laser light is highly absorbed by fluid in the volume.
22. An apparatus for cutting or ablating hard tissue, comprising: a
diode light pump disposed within an optical cavity and optically
aligned to light pump a gain medium within the optical cavity to
generate at least one pulse of electromagnetic energy having a
full-width half-max range closer to a beginning than an end of the
pulse the apparatus being configured to direct the electromagnetic
energy into a volume in close proximity to the hard tissue so that
the hard tissue is cut or ablated, wherein the generated laser
light has a wavelength, pulse, and power density suitable for
cutting and ablating tooth tissue.
23. An apparatus for cutting or ablating hard tissue comprising: a
diode light pump disposed within an optical cavity and optically
aligned to light pump a gain medium within the optical cavity to
generate at least one pulse of electromagnetic energy having a
full-width half-max range closer to a beginning than an end of the
pulse the apparatus being configured to direct the electromagnetic
energy into a volume in close proximity to the hard tissue so that
the hard tissue is cut or ablated, wherein the generated laser
light has a wavelength, pulse, and power density suitable for
cutting and ablating bone.
24. An apparatus for cutting or ablating hard tissue comprising: a
diode light pump disposed within an optical cavity and optically
aligned to light pump a gain medium within the optical cavity to
generate at least one pulse of electromagnetic energy having a
full-width half-max range closer to a beginning than an end of the
pulse, the apparatus being configured to direct the electromagnetic
energy into a volume in close proximity to the hard tissue so that
the hard tissue is cut or ablated, wherein temporal pulse control
is used to attain a uniform temporal pulse pattern.
25. The apparatus as set forth in claim 24, wherein gain switching
or Q-switching is used in attaining the uniform temporal pulse
pattern.
26. An apparatus for cutting or ablating hard tissue, comprising: a
diode light pump disposed within an optical cavity and optically
aligned to light pump a gain medium within the optical cavity to
generate at least one pulse of electromagnetic energy having a
full-width half-max range closer to a beginning than an end of the
pulse, the apparatus being configured to direct the electromagnetic
energy into a volume in close proximity to the hard tissue so that
the hard tissue is cut or ablated, wherein the diode light pump
comprises a diode array.
27. The apparatus as set forth in claim 26, wherein the diode light
pump is optically aligned to side pump the gain medium.
28. The apparatus as set forth in claim 27, wherein the gain medium
comprises a laser rod.
29. The apparatus as set forth in claim 28, wherein the gain medium
comprises an Erbium-based laser rod.
30. The apparatus as set forth in claim 27, wherein the gain medium
comprises an Erbium-based crystalline laser rod for generating
laser light in a range between 1.73 and 2.94 microns.
31. The apparatus as set forth in claim 27, wherein the
electromagnetic energy is generated in the TEMoo mode to attenuate
thermal effects.
32. The apparatus as set forth in claim 27, wherein the generated
electromagnetic energy has a wavelength, pulse, and power density
suitable for cutting and ablating tooth tissue.
33. The apparatus as set forth in claim 27, wherein the generated
electromagnetic energy has a wavelength, pulse, and power density
suitable for cutting and ablating bone.
34. The apparatus as set forth in claim 27, wherein temporal pulse
control is used to attain a uniform temporal pulse pattern.
35. The apparatus as set forth in claim 34, wherein gain switching
or Q-switching is used in attaining the uniform temporal pulse
pattern.
36. The method as set forth in claim 26, wherein the
electromagnetic energy has a wavelength in a range from about 2.69
um to about 2.95 um.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of co-pending U.S.
application Ser. No. 10/178,080, filed Jun. 21, 2002 and entitled
HIGH-EFFICIENCY, SIDE-PUMPED DIODE LASER SYSTEM (Att. Docket
B19280P), which is commonly assigned and the contents of which are
expressly incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates generally to cutting devices
and, more particularly, to diode laser systems.
[0004] 2. Description of Related Art
[0005] A solid-state laser system generally comprises a laser rod
for emitting coherent light and a stimulation source for
stimulating the laser rod to emit the coherent light. Flashlamps
are typically used as stimulation sources. Diodes may also be used
for the excitation source. The use of diodes for generating light
amplification by stimulated emission is discussed in the book
Solid-State Laser Engineering, Fourth Extensively Revised and
Updated Edition, by Walter Koechner, published in 1996.
[0006] Prior art laser diode pumped lasers have been either
end-pumped, as demonstrated in FIG. 1a or side-pumped. End pumping
configurations can be more efficient and can produce a better
transverse mode. In FIG. 1a, wherein "HR" denotes a high
reflectivity element and "OC" denotes an output coupling element,
laser output is focused into a fiber via a lens. Side pumping
constructions, on the other hand, can be more scalable therefore
enabling the generation of relatively high laser power and
energy.
SUMMARY OF THE INVENTION
[0007] In accordance with one aspect of the present invention, a
method of cutting or ablating hard tissue is disclosed, comprising
the steps of providing a gain medium, a diode, and an optical
cavity; placing the gain medium and the diode within the optical
cavity so that the diode array is optically aligned to pump the
gain medium; activating the diode to light pump the gain medium and
generate laser light; and directing the laser light onto the hard
tissue to cut or ablate the hard tissue.
[0008] In accordance with another aspect of the present invention,
a method of cutting or ablating hard tissue comprises the steps of
providing a gain medium, a diode light pump, and an optical cavity;
placing the gain medium and the diode light pump within the optical
cavity so that the diode light pump is optically aligned to light
pump the gain medium; activating the diode light pump to light pump
the gain medium and generate laser light; and directing the laser
light onto the hard tissue to cut or ablate the hard tissue.
[0009] According to another aspect of the invention, an apparatus
for cutting or ablating hard tissue comprises an optical cavity; a
gain medium disposed within the optical cavity; a diode light pump
disposed within the optical cavity and optically aligned to light
pump the gain medium to generate laser light, wherein the generated
laser light has a wavelength and power density suitable for cutting
and ablating hard tissue.
[0010] While the apparatus and method has or will be described for
the sake of grammatical fluidity with functional explanations, it
is to be expressly understood that the claims, unless expressly
formulated under 35 USC 112, are not to be construed as necessarily
limited in any way by the construction of "means" or "steps"
limitations, but are to be accorded the full scope of the meaning
and equivalents of the definition provided by the claims under the
judicial doctrine of equivalents, and in the case where the claims
are expressly formulated under 35 USC 112 are to be accorded full
statutory equivalents under 35 USC 112.
[0011] Any feature or combination of features described herein are
included within the scope of the present invention provided that
the features included in any such combination are not mutually
inconsistent as will be apparent from the context, this
specification, and the knowledge of one skilled in the art. In
addition, any feature or combination of features may be
specifically excluded from any embodiment of the present invention.
For purposes of summarizing the present invention, certain aspects,
advantages and novel features of the present invention are
described. Of course, it is to be understood that not necessarily
all such aspects, advantages or features will be embodied in any
particular implementation of the present invention. Additional
advantages and aspects of the present invention are apparent in the
following detailed description and claims.
BRIEF DESCRIPTION OF THE FIGURES
[0012] FIG. 1a is a schematic illustration of an end-pumped diode
laser in accordance with the prior art;
[0013] FIG. 1b is a side-pumped diode laser according to the
present invention;
[0014] FIG. 2a is a schematic top view of a laser head according to
the present invention;
[0015] FIG. 2b is a schematic side view of a laser head according
to the present invention;
[0016] FIG. 3 is a regulated laser pulse format according to the
present invention;
[0017] FIG. 4a shows the population inversion in a CW pumping
regime according to the present invention;
[0018] FIG. 4b shows the resonator Q due to the Q-switch hold-off
according to the present invention;
[0019] FIG. 4c shows the resulting laser pulse from FIGS. 4a and 4b
according to the present invention;
[0020] FIG. 5a shows the quasi CW current supplied to the pumping
laser diode according to the present invention;
[0021] FIG. 5b shows the population inversion in the quasi CW
pumping according to the present invention;
[0022] FIG. 5c shows resulting laser pulse from FIGS. 5a and 5b
according to the present invention;
[0023] FIG. 6 is a representation corresponding to a preferred
pulse shape; and
[0024] FIG. 7 is a close-up view of a pulse of FIG. 6a;
[0025] FIG. 8 is a block diagram showing fluid used in combination
with a laser in accordance with an embodiment of the present
invention; and
[0026] FIG. 9 is a plot of output optical energy versus time for a
laser system in accordance with an aspect of the present
invention.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
[0027] Reference will now be made in detail to particular
embodiments of the invention, examples of which are illustrated in
the accompanying drawings. Wherever possible, the same or similar
reference numbers are used in the drawings and the description to
refer to the same or like parts. It should be noted that the
drawings are in simplified form and are not to precise scale. In
reference to the disclosure herein, for purposes of convenience and
clarity only, directional terms, such as, top, bottom, left, right,
up, down, over, above, below, beneath, rear, and front, are used
with respect to the accompanying drawings. Such directional terms
should not be construed to limit the scope of the invention in any
manner.
[0028] Although the disclosure herein refers to certain illustrated
embodiments, it is to be understood that these embodiments are
presented by way of example and not by way of limitation. The
intent of the following detailed description, although discussing
exemplary embodiments, is to be construed to cover all
modifications, alternatives, and equivalents of the embodiments as
may fall within the spirit and scope of the invention as defined by
the appended claims.
[0029] In accordance with one aspect of the present invention, a
method of cutting or ablating hard tissue is disclosed, comprising
the steps of providing a gain medium, a diode array, and an optical
cavity; placing the gain medium and the diode array within the
optical cavity so that the diode array is optically aligned to side
pump the gain medium; activating the diode array to light pump the
gain medium and generate laser light; and directing the laser light
onto the hard tissue to cut or ablate the hard tissue.
[0030] In accordance with another aspect of the present invention,
a method of cutting or ablating hard tissue comprises the steps of
providing a gain medium, a diode light pump, and an optical cavity;
placing the gain medium and the diode light pump within the optical
cavity so that the diode light pump is optically aligned to light
pump the gain medium; activating the diode light pump to light pump
the gain medium and generate laser light; and directing the laser
light onto the hard tissue to cut or ablate the hard tissue.
[0031] According to another aspect of the invention, an apparatus
for cutting or ablating hard tissue, comprises an optical cavity; a
gain medium disposed within the optical cavity; a diode light pump
disposed within the optical cavity and optically aligned to light
pump the gain medium to generate laser light, wherein the generated
laser light has a wavelength and power density suitable for cutting
and ablating hard tissue.
[0032] In any of the above aspects, the gain medium may comprise a
laser rod, such as an Erbium-based laser rod. More particularly,
the gain medium may comprise an Erbium-based crystalline laser rod
for generating laser light in a range between 1.73 and 2.94
microns. The laser light can be generated in the TEMoo mode to
overcome thermal effects. In accordance with a method of the
present invention, the hard tissue can comprise, for example, tooth
or bone tissue. Temporal pulse control can be used to attain a
uniform temporal pulse pattern. In another embodiment, gain
switching or Q-switching can be used to attain the uniform temporal
pulse pattern. The diode light pump can comprise a diode array, and
the diode array can be optically aligned to side pump the gain
medium. The diode light pump can be placed within the optical
cavity so that the diode array is optically aligned to side pump
the gain medium.
[0033] Any feature or combination of features described herein are
included within the scope of the present invention provided that
the features included in any such combination are not mutually
inconsistent as will be apparent from the context, this
specification, and the knowledge of one of ordinary skill in the
art.
[0034] The methods and apparatuses of this application are intended
for use, to the extent the technology is compatible, with existing
technologies including the apparatuses and methods disclosed in any
of the following patents and patent applications: U.S. Pat. No.
5,741,247; U.S. Pat. No. 5,785,521; U.S. Pat. No. 5,968,037; U.S.
Pat. No. 6,086,367; U.S. Pat. No. 6,231,567; and U.S. Ser. No.
09/848,010 (filed May 2, 2001), which incorporates by reference the
disclosure of U.S. Pat. No. 6,288,499, all of which are assigned to
BioLase Technology, Inc. and are incorporated herein by reference.
The referenced U.S. Pat. No. 6,288,499 discloses an electromagnetic
energy source (e.g., laser) that generates an output optical energy
distribution including an output pulse of optical energy having a
full-width half-max ranges closer to a beginnings than an ends of
the output pulses of optical energy and also discloses full-width
half-max values of the output pulse ranging from about 0.025 to
about 250 microseconds.
[0035] The diode side pumped Erbium crystalline laser of the
present invention may emit at wavelengths between 1.73 and 2.94
.mu.m. The pumping may be accomplished by InGaAs laser diodes
configured as bars or arrays emitting at 968 nm, and can be
delivered in either a CW (continuous wave) or a QCW
(quasi-continuous wave) mode of operation, at power levels that may
begin at 40 W. With an optimized output coupling, the
light-to-light efficiency can be at least 10% and can reach a
magnitude up to 35%. One of the embodiments of this invention is
that these efficiency magnitudes are higher than those which may
have been previously attained, owing to the inventive design which
seeks to maximize the pump-to-laser mode overlap and to optimize
outcoupling, specifically tailoring the outcoupling to the pulse
format or CW operation of the laser.
[0036] The oscillator of the present invention is a plano-plano
resonator comprising a high reflectivity mirror and an outcoupling,
partially transmitting mirror. For certain applications intracavity
elements, such as an electro-optic or acousto-optic cell for
Q-switching, or an etalon for wavelength tuning can be introduced.
The laser can emit energy in, for example, one of the following
modes of operation: CW, gain switched obtained by quasi-CW
operation of the pump laser diode, and Q-switched by an
acousto-optical (AO) device or Q-switched by an electro-optical
(EO) device. Thermal management and temperature control are
provided by either air and/or water cooling, with the possibility
of using thermo-electric cooling.
[0037] In the category of the disclosed diode side pumped lasers
included are the following crystals: Er:LiYF.sub.4 (Er:YLF)
emitting at 1.73 .mu.m on the Er.sup.3+4I.sub.13/2.sup.4I.sub.15/2
transition; Er:LiYF.sub.4 emitting at 2.80 .mu.m on the
Er.sup.3+4I.sub.11/2.sup.4I.sub.13/2 transition;
Er:Y.sub.3Sc.sub.2GasO.sub.12 (Er:YSGG) emitting at 2.79 .mu.m on
the Er.sup.3+4I.sub.11/2.sup.4I.sub.13/2 transition;
Er:Gd.sub.3Sc.sub.2GasO.sub.12 (Er:GSGG) emitting at 2.8 .mu.m on
the Er.sup.3+4I.sub.11/2.sup.4I.sub.13/2 transition;
Er:Gd.sub.3GasO.sub.12 (Er:GGG) emitting at 2.82 .mu.m on the
Er.sup.3+4I.sub.11/2.sup.4I.sub.13/2 transition;
Er,Tm:Y.sub.3Al.sub.5O.sub.12 (TE:YAG) emitting at 2.69 .mu.m on
the Er.sup.3+4I.sub.11/2.sup.4I.sub.13/2 transition; Er:KYF.sub.4
emitting at 2.81 .mu.m on the Er.sup.3+4I.sub.11/2.sup.4I.sub.13/2
transition; Ho,Yb:KYF.sub.4 emitting at 2.84 .mu.m on the
Ho.sup.3+5I.sub.6.sup.5I.sub.7 transition;
Er:Y.sub.3Al.sub.5O.sub.12 (Er:YAG) emitting at 2.94 .mu.m on the
Er.sup.3+4I.sub.11/2.sup.4I.sub.13/2 transition;
Er:Y.sub.3AlO.sub.3 (Er:YALO) emitting at 2.71 .mu.m on the
Er.sup.3+4I.sub.11/2.sup.4I.sub.13/2 transition;
Er:KGd(WO.sub.4).sub.s (Er:KGW) emitting at 2.8 .mu.m on the
Er.sup.3+4I.sub.11/2.sup.4I.sub.13/2 transition;
Er:KY(WO.sub.4).sub.s (Er:KYW); Er:Al.sub.3O.sub.3 emitting on the
Er.sup.3+4I.sub.11/2.sup.4I.sub.13/2 transition; Er:Lu.sub.3O.sub.3
emitting at emitting at 2.7 .mu.m on the
Er.sup.3+4I.sub.11/2.sup.4I.sub.13/2 transition; Er:CaF.sub.2
emitting at 2.75-2.85 .mu.m on the
Er.sup.3+4I.sub.11/2.sup.4I.sub.13/2 transition;
Cr,Tm,Er:Y.sub.3Al.sub.5O.sub.12 (CTE:YAG) emitting at 2.7 .mu.m on
the Er.sup.3+4I.sub.11/2.sup.4I.sub.13/2 transition;
Er:BaLu.sub.2F.sub.8 emitting at 2.8 .mu.m on the
Er.sup.3+4I.sub.11/2.sup.4I.sub.13/2 transition;
Er:BaY.sub.2F.sub.8 (Er:BYF) emitting at 2.7 .mu.m on the
Er.sup.3+4I.sub.11/2.sup.4I.sub.13/2 transition; and Cr:ZnSe
emitting at 2-3 .mu.m.
[0038] Due to their efficient interaction with biological tissue
and water, these lasers are useful as surgical instruments, in the
areas of, for example, dental surgery, orthopedic surgery, tissue
ablation, bone cutting and soft tissue surfacing. Particular
applications may include use of the laser for expansion of atomized
water or fluid particles above a target surface for mechanical
cutting or ablation, such as disclosed in U.S. Pat. No. 5,741,247,
entitled Atomized Fluid Particles for Electromagnetically Induced
Cutting, and U.S. Pat. No. 5,785,521, entitled "Fluid Conditioning
System," the contents of which are expressly incorporated herein by
reference.
[0039] Another embodiment of the side diode pumped erbium lasers
and Ho,Yb:KYF4 laser is that when operated in pulses, the pulsed
format is highly repetitive in time and intensity. This performance
can facilitate precise and predictable cutting, and can improve
cutting efficiency. In dental and medical applications, this
feature is consistent with less heat or thermal denaturation of the
tissue, which can provide for quicker healing.
[0040] The present invention is configured as shown in FIGS. 1a, 2a
and 2b. It applies the side-pumped configuration to: 1) pumping of
erbium and Ho,Yb:KYF4 crystals to extract laser emission in the
1.73 and 2.94 .mu.m range, 2) dental and medical cutting and
resurfacing by mainly the 2.69 to 2.95 .mu.m range, 3) optimization
of the dental and medical process by efficient delivery of the
laser to the target and minimal thermal process. Configuration of
the crystal itself can be rectangular or round. A rectangular shape
may be preferred in one embodiment, although a cylindrical shape
may function well in modified embodiments. The pumping wavelength
should be chosen to be efficiently transferred into the crystal,
wherein for example the radiation wavelength of the diode pumping
source matches a peak absorption of the active media or crystal. In
one embodiment a lens may be used to couple the pump source to the
laser rod. Cooling sources and/or lenses may be positioned between
the pump source and the laser rod. Regarding FIGS. 2a and 2b, FIG.
2a is a schematic top view of a laser head according to the present
invention wherein "TEC" denotes thermo electric cooler, and FIG. 2b
is a schematic side view of a laser head according to the present
invention wherein opposing ends of the laser rod are cut to the
Brewster angle to provide polarization.
[0041] Regarding the present invention's application of the
side-pumped configuration to optimize dental and medical processes
by efficient delivery of the laser to the target and minimal
thermal process, optimization is accomplished by radiating the
target with a train of well regulated pulses, as shown in FIG. 3.
What is shown is a sequence of narrow pulses, each having a
sufficiently high power, for instance 20 kW, and an energy of 8 mJ.
With a duty cycle of 0.02% this determines an average power of 4 W.
A number of methods may be employed to attain such a pulse format,
among them: gain switching and Q-switching by either an
electro-optical or an acousto-optical Q-switch.
[0042] The Q-switch temporal trace is shown in FIGS. 4a-4c, wherein
FIG. 4a shows the population inversion in a CW pumping regime, FIG.
4b shows the resonator Q due to the Q-switch hold-off, and FIG. 4c
corresponds generally to FIG. 3 and shows the resulting laser
pulse. The gain switch temporal trace is shown in FIGS. 5a-5c,
wherein FIG. 5a shows the quasi-CW (QCW) current supplied to the
pumping laser diode, FIG. 5b shows the population inversion in the
QCW pumping regime, and FIG. 5c shows the resulting laser pulse.
Because in gain switching the resonator Q is never spoiled, the
pulse evolves simultaneously with the buildup of the population
inversion. Hence, the dynamics are similar to a free running laser,
as in the pulse train shown in FIG. 6. However, as shown in FIG.
5a, the gain is dropped to below threshold once the first spike is
generated, thus a gain switch pulse is formed as the first spike
only, as shown in FIG. 7. Additional description is provided in the
following table.
Diode
Pumped Laser Parameters
[0043] TABLE-US-00001 parameter Range Embodiment Example Wavelength
1.5-6.0 .mu.m 2.6-3.0 .mu.m 2.78 .mu.m Pulse duration 0.1-1000
.mu.sec 0.1-5.0 .mu.sec 1 .mu.sec Pulse repetition rate 1-1000 Hz
1-200 Hz 100 Hz (or in envelopes of 5-20 pulses separated by 1.0-10
.mu.sec) Energy per pulse 3-1000 mJ 10-500 mJ 50-100 mJ Average
power 0.1-100 W 0.1-10 W 8 W Spot size 20-5000 .mu.m 50-1000 .mu.m
500 .mu.m
[0044] As mentioned above, particular applications of the current
invention may include use of the laser for expansion of atomized
water or fluid particles above a target surface for mechanical
cutting or ablation. The above-referenced U.S. Pat. No. 6,288,499
discloses (a) output optical energy distributions including output
pulses of optical (e.g., laser) energy having full-width half-max
ranges closer to beginnings than ends of the output pulses and (b)
full-width half-max values of the output pulses ranging from about
0.025 to about 250 microseconds.
[0045] With reference to FIG. 8, output pulses of output optical
energy distributions can be useful for maximizing a cutting effect
of an electromagnetic energy source 32, such as a laser driven by a
diode or flashlamp driving circuit 30, directed into a distribution
(e.g., an atomized distribution) of fluid particles 34 above a
target surface 36. An apparatus for directing output pulses of
electromagnetic energy into a distribution of fluid particles above
a target surface is disclosed in the mentioned U.S. Pat. No.
5,741,247. High-intensity leading micropulses 64, 66, and 68 (FIG.
9, infra) of the output pulse can be used to impart large amounts
of energy into fluid particles to thereby expand the fluid
particles and apply mechanical cutting forces to the target
surface. The trailing micropulses after the maximum micropulse 68
have been found to further enhance the cutting efficiency.
According to an aspect of the present invention, a single large
leading micropulse 68 may be generated or, alternatively, two or
more large leading micropulses 68 (or 64, 66, for example) may be
generated.
[0046] With reference to FIG. 9, an output optical energy
distribution over time of an electromagnetic energy source
according to an aspect of the present invention is illustrated at
60. In the illustrated embodiment, the pulse width is about 200
microseconds. The output optical energy distribution 60 comprises a
maximum value 62, a number of leading micropulses 64, 66, 68, and a
portion of generally declining optical energy 70. As illustrated in
FIG. 9, the micropulse 68 comprises a maximum value 62 which is at
or near the very beginning of the output pulse. Additionally, the
full-width half-max value of the output optical energy distribution
(e.g., output pulse) in FIG. 9 is approximately 70 microseconds.
Applicants' invention contemplates output pulses comprising
full-width half-max values greater than 0.025 microseconds. In some
embodiments, the full-width half-max values range from about 0.25
microseconds to about 250 microseconds and, more preferably, range
from 10 to 150 microseconds, but other ranges may also be possible.
Additionally, Applicants' invention contemplates an output pulse
width of between 0.25 and 300 microseconds, for example.
[0047] As used herein, the full-width half-max range is defined
from a beginning time, where the amplitude first rises above
one-half the peak amplitude, to an ending time, where the amplitude
falls below one-half the peak amplitude a final time during the
pulse width. The full-width half-max value is defined as the
difference between the beginning time and the ending time. The
location of the full-width half-max range along the time axis,
relative to the output pulse width, is closer to the beginning of
the pulse than the end of the pulse. The location of the full-width
half-max range is preferably within the first half of the pulse
and, more preferably, is within about the first third of the output
pulse along the time axis. Other locations of the full-width
half-max range are also possible in accordance with the present
invention. The beginning time of the full-width half-max range
preferably occurs within the first 10 to 15 microseconds and, more
preferably, occurs within the first 12.5 microseconds from the
leading edge of the output pulse. The beginning time, however, may
occur either earlier or later within the output pulse. The
beginning time is preferably achieved within the first tenth of the
pulse width.
[0048] In view of the foregoing, it will be understood by those
skilled in the art that the methods of the present invention can
facilitate formation of laser devices, and in particular
side-pumped diode laser systems. The above-described embodiments
have been provided by way of example, and the present invention is
not limited to these examples. Multiple variations and modification
to the disclosed embodiments will occur, to the extent not mutually
exclusive, to those skilled in the art upon consideration of the
foregoing description. Such variations and modifications, however,
fall well within the scope of the present invention as set forth in
the following claims.
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