U.S. patent application number 10/102208 was filed with the patent office on 2002-12-26 for tunable laser.
Invention is credited to Little, Michael J..
Application Number | 20020196817 10/102208 |
Document ID | / |
Family ID | 27375018 |
Filed Date | 2002-12-26 |
United States Patent
Application |
20020196817 |
Kind Code |
A1 |
Little, Michael J. |
December 26, 2002 |
Tunable laser
Abstract
A tunable laser system is provided which includes a tunable
laser. The tunable laser combines a laser with a compliant
mechanism.
Inventors: |
Little, Michael J.; (Oak
Park, CA) |
Correspondence
Address: |
FLESHNER & KIM, LLP
P.O. Box 221200
Chantilly
VA
20153-1200
US
|
Family ID: |
27375018 |
Appl. No.: |
10/102208 |
Filed: |
March 21, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10102208 |
Mar 21, 2002 |
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10085143 |
Mar 1, 2002 |
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60284943 |
Apr 20, 2001 |
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60303772 |
Jul 10, 2001 |
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Current U.S.
Class: |
372/20 |
Current CPC
Class: |
G02B 6/3574 20130101;
G02B 6/4226 20130101; G02B 26/0841 20130101; G02B 2006/12104
20130101; B81B 2203/053 20130101; G02B 6/358 20130101; B81B
2203/058 20130101; G02B 6/3522 20130101; G02B 6/3528 20130101; B81B
3/0021 20130101; G02B 26/02 20130101; B81B 2201/047 20130101; G02B
6/3584 20130101; G02B 6/3572 20130101; G02B 6/3512 20130101; G02B
6/3526 20130101; G02B 6/3534 20130101; G02B 26/001 20130101; G02B
6/357 20130101 |
Class at
Publication: |
372/20 |
International
Class: |
H01S 003/10 |
Claims
What is claimed is:
1. A tunable laser system, comprising: a laser; and at least one
compliant mechanism configured to vary a wavelength of light output
by the laser.
2. The tunable laser system according to claim 1, wherein the laser
is a semiconductor laser.
3. The tunable laser system according to claim 1, wherein the
compliant mechanism comprises a mirror, and varying the position of
the mirror varies a wavelength output by the laser.
4. The tunable laser system according to claim 3, wherein the
compliant mechanism comprises a compliant support to which the
mirror is fixed, and at least a portion of the compliant support is
substantially flexible.
5. The tunable laser system according to claim 3, wherein the
compliant mechanism comprises a compliant support to which the
mirror is fixed, and at least a portion of the compliant support
comprises silicon, and another portion of the compliant optical
support comprises a compliant material.
6. The tunable laser system according to claim 5, wherein the
compliant material comprises an elastomer.
7. The tunable laser system according to claim 3, wherein the
mirror is movable by an actuator.
8. The tunable laser system according to claim 7, wherein the
compliant support comprises: an island, to which the mirror is
affixed; and a frame, wherein the island and the frame are flexibly
joined by a compliant member.
9. The tunable laser system according to claim 8, wherein at least
a portion of the actuator is attached to the island.
10. The tunable laser system according to claim 8, wherein the
compliant member comprises an elastomer.
11. The tunable laser system according to claim 8, wherein the
island and the frame comprise silicon.
12. The tunable laser system according to claim 8, wherein the
actuator comprises: a plurality of electrodes positioned on a
surface of the island opposite a surface to which the second mirror
is attached; and an electrode disposed on an actuator support.
13. The tunable laser system according to claim 12, wherein the
actuator support comprises silicon.
14. The tunable laser system according to claim 1, further
comprising an output optical fiber into which output light is
directed.
15. The tunable laser system according to claim 14, further
comprising: a lens configured to focus light into the output
optical fiber.
16. The tunable laser system according to claim 1, further
comprising: a lens configured to collimate light output by the
laser.
17. The tunable laser system according to claim 1, wherein the
compliant mechanism is positioned between the laser and an output
optical fiber.
18. The tunable laser system according to claim 1, wherein the
laser is positioned between the compliant mechanism and an output
optical fiber.
19. The tunable laser system according to claim 3, wherein the
mirror is curved.
20. The tunable laser system according to claim 19, wherein the
laser is positioned between the compliant mechanism and an output
optical fiber.
21. The tunable laser system according to claim 1, wherein the at
least one compliant mechanism comprises two compliant
mechanisms.
22. The tunable laser system according to claim 21, wherein the
laser is positioned between the two compliant mechanisms.
23. The tunable laser system according to claim 22, wherein the
laser comprises an anti-reflective on one end and an approximately
30% reflective coating on the other end.
24. The tunable laser system according to claim 21, further
comprising: an output optical fiber positioned to receive output
light.
25. The tunable laser system according to claim 24, further
comprising: a lens configured to focus the output light into the
output optical fiber.
26. The tunable laser system according to claim 21, wherein the two
compliant mechanisms each comprise a mirror, and wherein varying
the position of either mirror varies a wavelength output by the
tunable laser.
27. The tunable laser system according to claim 26, wherein each
mirror is curved.
28. The tunable laser system according to claim 1, wherein the
laser comprises a first fixed mirror and an active region, and the
compliant mechanism further comprises a second mirror mounted
thereon, wherein a first laser cavity is formed between the first
and second mirror, and wherein adjusting the position of the second
mirror varies a wavelength of light output by the tunable
laser.
29. The tunable laser system according to claim 28, wherein the
compliant mechanism further comprising a partially reflective
coating, wherein a second laser cavity is formed between the
partially reflective coating and the first mirror, which is tunable
by adjusting the position of the partially reflective coating, and
wherein a third laser cavity is formed between the partially
reflective coating and the second mirror, which is tunable by
adjusting the position of the second mirror.
30. A tunable laser, comprising: a first fixed mirror; a second
mirror mounted on a compliant mechanism; and an active region
formed between the first and second mirrors.
31. The tunable laser according to claim 20, wherein varying the
position of the second mirror varies a wavelength output by the
tunable laser.
32. A telecommunication system comprising the tunable laser system
of claim 1.
Description
[0001] This application is a continuation-in-part of U.S. patent
application Ser. No. 10/085,143 (Attorney Docket No. SMT-0039)
filed Mar. 1, 2002, entitled "Compliant Mechanism and Method of
Forming Same", which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention relates to a tunable laser.
[0004] 2. Background of the Related Art
[0005] There is a continuing need for tunable optical components
for various applications, such as optical networking,
wavelength-division-mul- tiplexing and other telecommunications
applications. In particular, numerous companies are developing
tunable lasers for use in such applications.
[0006] Existing technologies for tunable optical components are
either too costly, unreliable, or do not exhibit the performance
needs for present and/or future systems requirements.
[0007] The above references are incorporated by reference herein
where appropriate for appropriate teachings of additional or
alternative details, features and/or technical background.
SUMMARY OF THE INVENTION
[0008] An object of the invention is to solve at least the above
problems and/or disadvantages and to provide at least the
advantages described hereinafter.
[0009] The invention relates to a tunable laser. More particularly,
the invention relates to a tunable laser employing a compliant
mechanism that provides precise angular and longitudinal control
and reconfiguration.
[0010] Additional advantages, objects, and features of the
invention will be set forth in part in the description which
follows and in part will become apparent to those having ordinary
skill in the art upon examination of the following or may be
learned from practice of the invention. The objects and advantages
of the invention may be realized and attained as particularly
pointed out in the appended claims.
[0011] Additional advantages, objects, and features of the
invention will be set forth in part in the description which
follows and in part will become apparent to those having ordinary
skill in the art upon examination of the following or may be
learned from practice of the invention. The objects and advantages
of the invention may be realized and attained as particularly
pointed out in the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The invention will be described in detail with reference to
the following drawings in which like reference numerals refer to
like elements wherein:
[0013] FIG. 1 is a schematic cross-sectional side view of a
compliant mechanism according to an embodiment of the
invention;
[0014] FIGS. 1A and 1B show a plan view of exemplary electrodes of
a compliant mechanism according to an embodiment of the
invention;
[0015] FIG. 2 is a schematic cross-sectional side view of a
compliant mechanism according to an embodiment of the invention,
showing the island of the compliant mechanism in a tilted
configuration;
[0016] FIG. 3 is a schematic side view of a tunable laser system
according to an embodiment of the invention;
[0017] FIG. 4 is a schematic side view of a tunable laser system
according to another embodiment of the invention;
[0018] FIG. 5 is a schematic side view of a tunable laser system
according to an additional embodiment of the invention;
[0019] FIG. 6 is a schematic side view of a tunable laser system
according to still another embodiment of the invention;
[0020] FIG. 7 is an explanatory diagram detailing laser operation
with respect to the invention; and
[0021] FIG. 8 is an explanatory chart comparing features of
embodiments of the present invention to current laser
technologies.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0022] Most tuneable lasers available today function at power
levels of approximately 1 to 2 milliwatts (mW). However, what is
needed for most telecom applications is a high-power tuneable
laser, more particularly, a tunable laser that can function at
power levels of 20 to 50 mW. The most popular tunable lasers are
fabricated with vertical cavity surface-emitting lasers (VCSELs),
which are intrinsically low-power. Only edge-emitting laser
technology is capable of the high powers necessary for most telecom
applications. However, traditional edge-emitting lasers are fixed
wavelength devices. They can be made tunable by adding external
components. However, known external tuning devices are too
expensive, too fragile, or lack other desired performance
characteristics.
[0023] High-power tunable lasers have been developed which package
tunable mirrors with edge-emitting lasers. However, these known
designs are complex, fragile, and expensive. The tunable laser
according to the invention combines an off-the-shelf, edge-emitting
laser with a compliant mechanism, as discussed below, producing a
variable wavelength, robust high-power laser.
[0024] The optical spectrum of a laser depends on the particular
characteristics of the optical cavity of the laser. An optical wave
propagating through the laser cavity forms a standing wave between
two mirror facets of the laser. This standing wave resonates only
when the cavity length L is an integer number M of half wavelengths
existing between the two mirrors. When the standing wave resonates,
laser light is emitted at the resonant wavelength. The present
invention varies the cavity length L of a laser cavity of a laser
using a compliant mechanism, thereby varying the wavelength of the
light emitted by the laser.
[0025] FIGS. 3, 4, 5, and 7 each show a tunable laser system
employing a compliant mechanism, according to embodiments of the
invention. Each of these embodiments will be discussed below in
turn. As stated, each embodiment employs a compliant mechanism. A
compliant mechanism is described in co-pending parent U.S. patent
application Ser. No. 10/085,143 (Attorney Docket No. SMT-0039)
filed Mar. 1, 2002, entitled "Compliant Mechanism and Method of
Forming Same", which is hereby incorporated by reference. Any of
the embodiments disclosed in U.S. patent application Ser. No.
10/085,143 (Attorney Docket No. SMT-0039) can be employed to
realize the apparatus and methods according to the invention
discussed herein.
[0026] FIG. 1 also shows a compliant mechanism 10 employable in the
tunable lasers, according to the invention. In the compliant
mechanism 10 of FIG. 1, a complaint support 20 supports an optical
component, such as mirror 25. The compliant support 20 is formed of
a frame 20B, an island 20A, and a compliant member 50, which
attaches the island 20A to the frame 20B, and provides flexibility
therebetween. The mirror 25, which is affixed to the island 20A of
the compliant support 20, is movable via an actuator 60, which will
be further discussed hereafter.
[0027] The frame 20B and the island 20A of the compliant support 20
are preferably formed of a generally inflexible material,
preferably a material that is compatible with
micro-electro-mechanical systems fabrication processes, such as
silicon. However, other materials, generally or partially flexible,
may also be appropriate. The compliant member 50 is formed of a
flexible material, preferably a highly compliant polymeric
material, such as an elastomer. However, other materials may also
be appropriate.
[0028] In operation, the actuator 60 can be controlled to apply a
force to the island 20A, thereby moving the island 20A, for
example, as shown in FIG. 2. The compliant member 50 exerts a
restoring force to the island 20A, which tends to urge the island
20A back into alignment with the frame 20B when the actuating force
is removed. The actuator 60 functions to move at least the island
20A, and can include any number and configuration of magnetic,
electrostatic, or mechanical force transducers.
[0029] In a preferred embodiment, the actuator 60 includes a first
set 40 of electrodes 40A positioned on a surface 21A of the island
20A opposite to a surface 21B on which the mirror 25 is positioned.
In one preferred embodiment, an anti-reflection (AR) coating 45 is
provided between the surface 21A of the island portion 20A and the
electrodes 40A.
[0030] The actuator 60 further includes a common electrode 35A
positioned on a surface 31A of an actuator support 30, according to
an embodiment of the invention. The actuator support 30 may include
a hole 325 for passing source light to the mirror 25. The actuator
support 30 is preferably formed of a generally inflexible material,
preferably a material that is compatible with
micro-electro-mechanical systems fabrication processes, such as
silicon. However, other materials, generally or partially flexible,
may also be appropriate. The complaint support 20 and the actuator
support 30 together form compliant mechanism 10, which is described
in detail in U.S. patent application Ser. No. 10/085,143 (Attorney
Docket No. SMT-0039).
[0031] FIGS. 1A and 1B show a plan view of the electrodes 40A and
35A. In this embodiment, three electrodes 40A are provided on the
compliant support 20 and one common electrode 35A is provided on
the actuator support 30. However, this arrangement could be
reversed. Further, a variety of other configurations of electrodes
which cooperatively function together could be utilized.
[0032] The electrodes 40A, 35A are configured to generate an
electrostatic force when a command signal is applied thereto. The
command signal can be configured to create a repulsive or an
attractive electrostatic force between the electrodes.
[0033] FIG. 3 is a schematic side view of a tunable laser system
100, according to an embodiment of the invention. The tunable laser
system 100 includes a tunable laser 101 formed of a compliant
mechanism 110, and a laser 115, for example, a semiconductor laser,
preferably mounted on a heat sink 120. As shown in FIG. 3, the
laser 115 includes an active region 135, and a high-reflectivity
(HR) coating 145, at one side thereof.
[0034] Mirror 125 is mounted on the island 111 of the compliant
mechanism 110. Mirror 125, active region 135, and HR coating 145
together form a (first) laser cavity, with mirror 125 functioning
as the output mirror of the laser cavity. By adjusting the position
of mirror 125, a length of the laser cavity can be varied, varying
the wavelength of light output by the tunable laser 101. A lens 130
is preferably positioned between the laser 115 and mirror 125 to
collimate the light from the laser 115.
[0035] The tunable laser system 100 may include an output optical
fiber 150 configured to receive light output by the tunable laser
101. Additionally, the tunable laser system 100 may include a lens
140, which functions to focus output light into the output optical
fiber 150.
[0036] Element 132 on the island 111 may be an anti-reflective
coating. Alternatively, element 132 may be a partially reflective
coating. In such an embodiment, partially reflective coating 132,
along with active region 135 and HR coating 145 form a second laser
cavity, while partially reflective coating 132 and mirror 125 form
a third laser cavity. The precise resonant wavelengths of the first
and second cavities can be adjusted by tuning the position of the
island 111, which tunes the position of both the mirror 125 and the
partially reflective coating 132, respectively, similar to the
embodiment of FIG. 6 discussed below. Because the mirror 125 and
the partially reflective coating 132 move together as the position
of the island 111 is tuned, the resonant wavelength of the third
laser cavity, formed by mirror 125 and partially reflective coating
132, remains substantially constant.
[0037] FIG. 4 is a schematic side view of a tunable laser system
200, according to another embodiment of the invention. The tunable
laser system 200 of FIG. 4 is similar to the tunable laser system
of FIG. 3. Similar reference numerals have been utilized to refer
to similar elements, and repetitive discussion has been
omitted.
[0038] The tunable laser system 200 includes a tunable laser 201.
The tunable laser 201 employs a compliant mechanism 210, and
includes a laser 215, for example, a semiconductor laser,
preferably mounted on a heat sink 220. As shown in FIG. 4, the
laser 215 includes an active region 235, and a mirror 245 at one
end.
[0039] The compliant mechanism 210 supports an HR mirror 225 which,
together with the active region 235 and mirror 245, forms a laser
cavity. By adjusting the position of the HR mirror 225, a length of
the laser cavity can be varied, thereby varying the wavelength of
light output by the tunable laser 201.
[0040] A lens 230 is preferably positioned between the laser 215
and mirror 225 to collimate the light from the laser 215.
Additionally, the tunable laser system 200 may include a lens 240,
which functions to focus output light into an (optional) output
optical fiber 250.
[0041] FIG. 5 is a schematic side view of a tunable laser system
300 according to another embodiment of the invention. The tunable
laser system 300 is similar to the tunable laser systems of FIGS. 3
and 4. Similar reference numerals have been utilized to refer to
similar elements, and repetitive discussion has been omitted.
[0042] The tunable laser system 300 of FIG. 5 includes a tunable
laser 301 comprised of a laser 315, for example, a semiconductor
laser, used in combination with a compliant mechanism 310. The
compliant mechanism of this embodiment differs from the compliant
mechanism of previously discussed embodiments in that the shape of
HR mirror 325 supported on the compliant mechanism 310 is adjusted
to provide a desired spatial mode of the laser light 305 output by
the tunable laser 301. For example, in this embodiment, the HR
mirror 325 is curved to provide a desired spatial mode of the
output laser light 325 for coupling to an output optical fiber 350.
The curvature of the HR mirror 325 eliminates the need for a
focusing lens. That is, the curved mirror functions to focus the
light.
[0043] FIG. 6 is a schematic side view of a tunable laser system
400, according to another embodiment of the invention. The tunable
laser system 400 of FIG. 6 is similar to the tunable laser systems
of FIGS. 3-5. Similar reference numerals have been utilized to
refer to similar elements, and repetitive discussion has been
omitted.
[0044] The tunable laser system 400 of FIG. 6 includes a tunable
laser 401, for example, a semiconductor laser, which utilizes two
compliant mechanism 410A and 410B. Laser 415, preferably provided
on a heat sink 420, is positioned between the complaint mechanism
410A and 410B. The laser system depicted in FIG. 6 is a double
resonant cavity design. One resonant cavity is formed by the gap
between mirror 425B and coating 446. Because the length of the
cavity is relatively short, the mode resonances are relatively
widely spaced as shown in FIG. 7(b). The precise resonant
wavelengths of this cavity are adjusted by tuning the position of
mirror 425B. The second cavity is formed by the gap between coating
446 and mirror 425A. This cavity, being longer, has more closely
spaced resonant modes, as indicated in FIG. 7(c). The precise
resonant wavelength of this cavity is tuned by adjusting the
position of mirror 425A. The gain profile of the laser's active
output is determined by the superposition of the spectra of the two
resonant cavities with the gain profile as shown in FIG. 7(d). If
the length of the second cavity is adjusted such that the resonant
wavelengths are equal to the International Telecommunication Union
(ITU) grid, then the laser is only capable of outputting at those
wavelengths. The length of the first resonant cavity is adjusted to
select which one of the ITU wavelengths will rise above the gain
threshold of the active medium.
[0045] The tunable laser system 400 of FIG. 7 may further include a
lens 440, which functions to focus light output by the tunable
laser 401 into an output optical fiber 450.
[0046] FIG. 8 is a chart comparing the present invention to current
laser technologies. In comparison to prior art VCSELs and
edge-emitting lens, the tunable laser of the present invention
provides a tuning range of approximately 40 mm, as well as a power
level of greater than approximately 25 mw.
[0047] The foregoing embodiments and advantages are merely
exemplary and are not to be construed as limiting the present
invention. The present teaching can be readily applied to other
types of apparatuses. The description of the present invention is
intended to be illustrative, and not to limit the scope of the
claims. Many alternatives, modifications, and variations will be
apparent to those skilled in the art. In the claims,
means-plus-function clauses are intended to cover the structures
described herein as performing the recited function and not only
structural equivalents but also equivalent structures.
* * * * *