Tunable laser

Abstract

A tunable laser system is provided which includes a tunable laser. The tunable laser combines a laser with a compliant mechanism.

Description

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-multiplexing 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.

Claims

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.