Ring Laser Gyroscope with an Active Volume Bragg Grating

Abstract

The present invention is entitled "Ring Laser Gyroscope with an Active Volume Bragg Grating". The present invention provides a ring laser gyroscope that includes: an optical block defining an optical closed-loop path; at least one mirror structure mounted on the optical block and in communication with the closed-loop path; at least one volume Bragg grating mounted on the optical block and in communication with the closed-loop path; and a pump laser in communication with the volume Bragg grating, the laser being configured to emit a light beam at a selected angle of incidence such that the light beam passes through the volume Bragg grating and overlaps with the closed-loop path. The volume Bragg grating serves as a gain medium to increase the optical power of the light beam and generate a pair of counter-propagating light beams within the closed-loop path. The mirror structure and the volume Bragg grating are positioned and angled to reflect the counter-propagating light beams so that they travel around the closed-loop path.

Description

BACKGROUND OF THE INVENTION

[0001] For many years, ring laser gyroscopes such as helium-neon (He-Ne) ring laser gyroscopes have been used in many navigation systems. The He-Ne ring laser gyroscope uses He-Ne gas as a gain medium to generate two-way laser light to detect the Sagnac phase shift due to rotation. Due to gas leakage, the gas nature of the gain medium requires complex processing techniques and has a limited lifespan.

[0002] Accordingly, there is a need for a solid-state material to be used as a gain medium in a ring laser gyroscope that will provide a longer lifespan and eliminate some of the bulky fixtures designed for gas lasers in ring laser gyroscopes. SUMMARY OF THE INVENTION

[0003] A ring laser gyroscope includes: an optical block defining an optical closed-loop path; at least one mirror structure mounted on the optical block and optically communicating with the optical closed-loop path; at least one volume Bragg grating mounted on the optical block and optically communicating with the optical closed-loop path; and a pump laser optically communicating with the volume Bragg grating, the pump laser configured to emit a light beam at a selected incident angle such that the light beam passes through the volume Bragg grating and overlaps with the optical closed-loop path. The volume Bragg grating acts as a gain medium to increase the optical power of the light beam and generates a pair of counter-propagating light beams within the optical closed-loop path from the light beam. The mirror structure and the volume Bragg grating are positioned and angled appropriately to reflect the counter-propagating light beams so that they travel around the optical closed-loop path. BRIEF DESCRIPTION OF THE DRAWINGS

[0004] It should be understood that the drawings illustrate only exemplary embodiments and should not be considered as limiting the scope of the invention. The exemplary embodiments will be described with additional features and details by the use of the drawings, wherein:

[0005] Figure 1 is a schematic diagram of a ring laser gyroscope implemented with an active volume Bragg grating according to one embodiment;

[0006] Figure 2A and Figure 2B is a schematic diagram of a volume Bragg grating that can be implemented in a ring laser gyroscope according to one embodiment;

[0007] Figure 3 is a schematic diagram of a ring laser gyroscope implemented with an active volume Bragg grating according to another embodiment;

[0008] Figure 4 is a schematic diagram of a ring laser gyroscope implemented with an active volume Bragg grating according to an alternative embodiment;

[0009] Figure 5 is a schematic diagram of a ring laser gyroscope implemented with multiple active volume Bragg gratings according to another embodiment;

[0010] Figure 6 is a schematic diagram of a ring laser gyroscope implemented with multiple active volume Bragg gratings according to an alternative embodiment; and

[0011] Figure 7 is a schematic diagram of a ring laser gyroscope implemented with multiple active volume Bragg gratings according to another embodiment. DETAILED DESCRIPTION

[0012] In the following detailed description, embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. It should be understood that other embodiments may be utilized without departing from the scope of the invention. Accordingly, the following detailed description should not be construed in a limiting sense.

[0013] Various embodiments of a ring laser gyroscope implemented with active volume Bragg gratings are described herein. In various embodiments, at least one high reflector in the ring laser gyroscope is replaced with an active volume Bragg grating made of a solid state material. The volume Bragg grating can serve simultaneously as a gain medium and a high reflector in the cavity of the ring laser gyroscope.

[0014] The volume Bragg grating differs from a conventional diffraction grating in that the grating structure of the volume Bragg grating is written inside a bulk glass material, rather than on the surface of the glass material as in a conventional diffraction grating. The volume Bragg grating is used to allow a light beam to penetrate into the bulk glass material and then be reflected or transmitted by the grating structure within the bulk glass material. When the light beam is reflected or transmitted by the grating structure in the volume Bragg grating, the light beam is also amplified because the volume Bragg grating serves as a gain medium.

[0015] Rare earth doped glass materials can be used to fabricate the volume Bragg gratings described herein. In various embodiments, the thickness of the volume Bragg grating can be from a few micrometers to several hundred micrometers. The volume Bragg grating is directly attached to the optical block of the ring laser gyroscope to replace a mirror or an output coupler. Using the volume Bragg grating in this way can reduce the assembly time and cost of the ring laser gyroscope.

[0016] More details of various embodiments are described below in conjunction with the drawings.

[0017] Figure 1FIG. 0 shows a ring laser gyroscope (RLG) 100 implemented with an active volume Bragg grating (VBG) 120 according to one embodiment. The RLG 100 includes an optical block 110 having a resonator in the form of an optical closed-loop path 112, which has a substantially triangular shape. A pair of mirror structures 114, 116 are mounted on the optical block 110 at the first and second corners of the closed-loop path 112, respectively. The VBG 120 is mounted at the third corner of the closed-loop path 112 and is optically communicable with the closed-loop path. The mirror structures 114, 116 together with the VBG 120 are positioned and angled appropriately to reflect light so that it travels around the closed-loop path 112.

[0018] A pump laser 130, such as a semiconductor laser, is configured to emit a beam 132 at a selected incident angle such that the beam 132 passes through the VBG 120 and overlaps with the closed-loop path 112 in the VBG 120. The VBG 120 is used as a gain medium that increases the optical power of the beam within the closed-loop path 112 and generates a pair of counter-propagating beams 134 within the closed-loop path 112. Through the reflections of the mirror structures 114, 116 and the VBG 120, the counter-propagating beams 134 travel in opposite directions (such as in the clockwise (CW) direction and the counterclockwise (CCW) direction) within the cavity of the closed-loop path 112.

[0019] The optical block 110 may be made of a transparent material such as a glass material. The mirror structures 114, 116 may each be, for example, a metal mirror, a multi-coated dielectric mirror, etc.

[0020] The VBG 120 may be made of a rare-earth doped glass (such as neodymium (Nd)-doped glass, ytterbium (Yb)-doped glass, erbium (Er)-doped glass, etc.) material. The VBG 120 may be written, for example, by direct laser scribing or by ultraviolet (UV) interference. The VBG 120 may be formed to simultaneously serve as a gain medium and a reflecting device for the beam emitted by the pump laser 130.

[0021] A photodetection device 140 is optically communicable with one of the mirror structures (such as the mirror structure 116), which acts as an optical coupler, such that a portion of the beam from the closed-loop path 112 is coupled out to the photodetection device 140. In this embodiment, the reflecting surface of the mirror structure 116 is partially light-transmissive, which allows a portion of the counter-propagating beams 134 in the closed-loop path 112 to pass through the mirror structure to reach the photodetection device 140.

[0022] During operation, rotation of the RLG 100 causes a change in the effective path length of the counter-propagating beams in the closed-loop path 112, thereby creating a frequency difference between the counter-propagating beams. The frequency difference produces an interference pattern that is detected by the photodetector 140. Subsequently, the corresponding output signal from the photodetector 140 is sent to a processor to determine the angular rate of rotation of the RLG 100.

[0023] Figure 2A and Figure 2B More details of the VBG 200 are shown, which is similar to the VBG 120 implemented in the RLG 100 as a gain medium and a reflecting device. The VBG 200 includes a glass block 210 (such as a rare-earth doped glass block) and a grating structure 212 written inside the glass block 210.

[0024] As Figure 2A shown, the grating structure 212 is configured to reflect the incident beam 230 if a given angle of incidence (θ1) satisfies the Bragg condition. As Figure 2B shown, for different angles of incidence (θ2), hardly any reflection occurs at the grating structure 212, and the incident beam 230 will pass through the VBG 200. These characteristics of the VBG 200 (and the VBG 120) allow such VBGs to be used simultaneously as a gain medium and a reflecting device in a ring laser gyroscope.

[0025] Figure 3 A ring laser gyroscope (RLG) 300 implemented with an active volume Bragg grating (VBG) 320 according to another embodiment is shown. The RLG 300 includes an optical block 310 having a resonator in the form of an optical closed-loop path 312 that has a substantially triangular shape. A pair of mirror structures 314, 316 are mounted on the optical block 310 at two corners of the closed-loop path 312, respectively. The VBG 320 is mounted at the third corner of the closed-loop path 312 and is optically connected to the closed-loop path. The mirror structures 314, 316 together with the VBG 320 are positioned and angled appropriately to reflect light so that it circulates around the closed-loop path 312.

[0026] As Figure 3 shown, the RLG 300 also includes a piezoelectric device 324 coupled to one end of the VBG 320. The piezoelectric device 324 can be made of a piezoelectric ceramic material (such as lead zirconate titanate (PZT)).

[0027] The pump laser 330 (such as a semiconductor laser) is configured to emit a light beam 332 at a selected incident angle such that the light beam 332 passes through the VBG 320 and overlaps with the closed-loop path 312 in the VBG 320. The VBG 320 is used as a gain medium for increasing the optical power of the light beam within the closed-loop path 312 and generating a pair of counter-propagating light beams 334 within the closed-loop path 312. Through the reflection of the mirror structures 314, 316, and the VBG 320, the counter-propagating light beams 334 travel in opposite directions (such as in the CW and CCW directions) within the cavity of the closed-loop path 312.

[0028] The optoelectronic detection device 340 is optically connected to one of the mirror structures in the mirror structure (such as the mirror structure 316), and this mirror structure acts as an optical coupler such that a part of the light beam from the closed-loop path 312 is coupled and output to the optoelectronic detection device 340. In this embodiment, the reflective surface of the mirror structure 316 is partially light-transmissive, which allows a part of the counter-propagating light beam 334 in the closed-loop path 312 to pass through this mirror structure and reach the optoelectronic detection device 340.

[0029] The piezoelectric device 324 is configured to provide cavity length control for adjusting the power of the light beam in the closed-loop path 312. By adding another piezoelectric device (such as a PZT) on the mirror structure 314 or the mirror structure (coupler) 316, the piezoelectric device 324 can be implemented to operate in a push-pull mode on the VBG 320, thereby reducing the gain grating effect while still maintaining the cavity length of the closed-loop path 312.

[0030] During operation, the rotational angular rate of the RLG 300 is determined in a similar manner as used above for the RLG 100.

[0031] Although Figure 1 and Figure 3 the illustrated ring laser gyroscope has a triangular configuration, in other embodiments, the ring laser gyroscope can have a square configuration, a rectangular configuration, a pentagonal configuration, a hexagonal configuration, or any other polygonal configuration including an optical closed-loop path.

[0032] For example, Figure 4Shows a ring laser gyroscope (RLG) 400 according to an alternative embodiment, which has a substantially rectangular (e.g., square) shape and is implemented by an active volume Bragg grating (VBG) 420. The RLG 400 includes an optical block 410 having a resonator in the form of an optical closed-loop path 412. A set of mirror structures 414, 416, and 418 are mounted on the optical block 410 at the first, second, and third corners of the closed-loop path 412, respectively. The VBG 420 is mounted at the fourth corner of the closed-loop path 412 and is optically connected to the closed-loop path. The mirror structures 414, 416, 418, together with the VBG 420, are positioned and angled appropriately to reflect light so that it travels around the closed-loop path 412.

[0033] The pump laser 430 (such as a semiconductor laser) is configured to emit a beam 432 at a selected incident angle such that the beam 432 passes through the VBG 420 and overlaps with the closed-loop path 412 in the VBG 420. The VBG 420 is used as a gain medium for increasing the optical power of the beam within the closed-loop path 412 and generating a pair of counter-propagating beams 434 within the closed-loop path 412. Through the reflections of the mirror structures 414, 416, 418, and the VBG 420, the counter-propagating beams 434 travel in opposite directions (such as in the CW and CCW directions) within the cavity of the closed-loop path 312.

[0034] The photodetector device 440 is optically connected to one of the mirror structures (such as the mirror structure 418), which acts as an optical coupler, such that a portion of the beam from the closed-loop path 412 is coupled out to the photodetector device 440. In this embodiment, the reflective surface of the mirror structure 418 is partially light-transmissive, which allows a portion of the counter-propagating beams 434 in the closed-loop path 412 to pass through the mirror structure to reach the photodetector device 440.

[0035] During operation, the rotational angular rate of the RLG 100 is determined in a manner similar to that used for the RLG 400 above.

[0036] Although Figure 1 , Figure 3 and Figure 4 the ring laser gyroscope shown utilizes a single volume Bragg grating, in other embodiments, the ring laser gyroscope can be configured to use multiple volume Bragg gratings. Examples of such embodiments are described below.

[0037] Figure 5FIG. 500 shows a ring laser gyroscope (RLG) implemented with multiple active volume Bragg gratings (VBGs) according to one embodiment. The RLG 500 includes an optical block 510 having a resonator in the form of an optical closed-loop path 512, which has a substantially triangular shape. A mirror structure 514 is mounted on the optical block 510 at one corner of the closed-loop path 512. A pair of VBGs 520, 522 are respectively mounted at the other corners of the closed-loop path 512 and are optically connected to the closed-loop path. The mirror structure 514 together with the VBGs 520, 522 are positioned and angled appropriately to reflect light so that it circulates around the closed-loop path 512.

[0038] A first pump laser 530 is configured to emit a first pump beam 532 at a selected incident angle such that the beam 532 passes through the VBG 520 and overlaps with the closed-loop path 512 in the VBG 520. A second pump laser 534 is configured to emit a second pump beam 536 at a selected incident angle such that the beam 536 passes through the VBG 522 and overlaps with the closed-loop path 512 in the VBG 522.

[0039] The VBGs 520, 522 are used to act as gain media to increase the optical power of the beam within the closed-loop path 512 and generate a pair of counter-propagating beams 538 within the closed-loop path 512. Through the reflections of the mirror structure 514 and the VBGs 520, 522, the counter-propagating beams 538 travel in opposite directions (such as in the CW and CCW directions) within the cavity of the closed-loop path 512.

[0040] A photodetector device 540 is optically connected to the mirror structure 514 acting as an optical coupler such that a portion of the beam from the closed-loop path 512 is coupled out to the photodetector device 540. In this embodiment, the reflective surface of the mirror structure 514 is partially light-transmissive, which allows a portion of the counter-propagating beams 538 in the closed-loop path 512 to pass through the mirror structure to reach the photodetector device 540.

[0041] During operation, the rotation angular rate of the RLG 500 is determined in a similar manner as used above for the RLG 100.

[0042] Figure 6Shows a ring laser gyroscope (RLG) 600 implemented with multiple active volume Bragg gratings (VBGs) according to an alternative embodiment. The RLG 600 includes an optical block 610 having a resonant cavity in the form of an optical closed-loop path 612. A mirror structure 614 is mounted on the optical block 610 at one corner of the closed-loop path 612. A pair of VBGs 620, 622 are respectively mounted at the other corners of the closed-loop path 612 and are optically communicative with the closed-loop path. The mirror structure 614 together with the VBGs 620, 622 are positioned and angled appropriately to reflect light to travel around the closed-loop path 612.

[0043] The pump laser 630 is configured to emit a pump beam 632 at a selected incident angle such that the beam 632 passes through the VBG 620 and overlaps with the closed-loop path 612 in the VBG 620. The VBG 620 is used as a gain medium for increasing the optical power of the beam within the closed-loop path 612 and generating a pair of counter-propagating beams 634 within the closed-loop path 612. Through the reflections of the mirror structure 614 and the VBGs 620, 622, the counter-propagating beams 634 travel in opposite directions (such as in the CW and CCW directions) within the cavity of the closed-loop path 612.

[0044] The photodetector device 640 is optically communicative with the mirror structure 614 acting as an optical coupler such that a portion of the beam from the closed-loop path 612 is coupled out to the photodetector device 640. In this embodiment, the reflective surface of the mirror structure 614 is partially light-transmissive, which allows a portion of the counter-propagating beams 634 in the closed-loop path 612 to pass through the mirror structure to reach the photodetector device 640.

[0045] In addition, the RLG 600 includes a pump mirror 650 located within the optical block 610. The mirror 650 is configured to reflect the residual light 636 of the portion of the pump beam 632 that passes through the VBG 620. The residual light 636 is reflected by the pump mirror 650 to the VBG 622, which is configured to allow the residual light 636 to pass through it for recycling during the operation of the RLG 600.

[0046] Figure 7Shows a ring laser gyroscope (RLG) 700 implemented with multiple active volume Bragg gratings (VBGs) according to another embodiment. The RLG 700 includes an optical block 710 having a resonator in the form of an optical closed-loop path 712, which has a substantially rectangular shape. A mirror structure 714 is mounted on the optical block 710 at one corner of the closed-loop path 712. A set of VBGs 720, 722, 724 are respectively mounted at the other corners of the closed-loop path 712 and are optically connected to the closed-loop path. The mirror structure 714 together with the VBGs 720, 722, 724 are positioned and angled appropriately to reflect light so that it travels around the closed-loop path 712.

[0047] As Figure 7 shown, the RLG 700 also includes a pair of piezoelectric devices 726, 728 coupled to the corresponding ends of the VBGs 620, 622. The piezoelectric devices 726, 728 can be made of (for example) PZT.

[0048] A first pump laser 730 is configured to emit a first pump beam 732 at a selected incident angle such that the beam 732 passes through the VBG 720 and overlaps with the closed-loop path 712 in the VBG 720. A second pump laser 734 is configured to emit a second pump beam 736 at a selected incident angle such that the beam 736 passes through the VBG 722 and overlaps with the closed-loop path 712 in the VBG 722.

[0049] The VBGs 720, 722 are used to act as gain media to increase the optical power of the beam within the closed-loop path 712 and generate a pair of counter-propagating beams 738 within the closed-loop path 712. Through the reflection of the mirror structure 714 and the VBGs 720, 722, 724, the counter-propagating beams 738 travel in opposite directions (such as in the CW and CCW directions) within the cavity of the closed-loop path 712.

[0050] A photodetector device 740 is optically connected to the mirror structure 714 acting as an optical coupler such that a portion of the beam from the closed-loop path 712 is coupled and output to the photodetector device 740. In this embodiment, the reflective surface of the mirror structure 714 is partially light-transmissive, which allows a portion of the counter-propagating beams 738 in the closed-loop path 712 to pass through the mirror structure to reach the photodetector device 740.

[0051] The piezoelectric devices 726, 728 are configured to provide cavity length control to adjust the power of the pump lasers 730, 734. The piezoelectric devices 726, 728 can be implemented to operate in a push-pull mode on the VBGs 720, 722, thereby reducing the gain grating effect while still maintaining the cavity length during the operation of the RLG 700.

[0052] Optionally, the RLG 700 may include a pump mirror 750 located within the optical block 710. The pump mirror 750 is configured to reflect residual light, such as residual light 737 from a portion of the pump beam 736 that passes through the VBG 722. The residual light 737 is reflected by the pump mirror 750 to the VBG 724, which is configured to allow the residual light 737 to pass therethrough for recycling during operation of the RLG 700. In another specific embodiment, the pump mirror 750 may be configured to direct residual light from a portion of the pump beam 732 that passes through the VBG 720 such that the residual light is sent to the VBG 724 for recycling.

[0053] Exemplary Embodiments

[0054] Embodiment 1 includes a ring laser gyroscope that includes: an optical block defining an optical closed-loop path; at least one mirror structure mounted on the optical block and optically communicating with the optical closed-loop path; at least one volume Bragg grating mounted on the optical block and optically communicating with the optical closed-loop path; and a first pump laser optically communicating with the volume Bragg grating, the first pump laser being configured to emit a beam at a selected angle of incidence such that the beam passes through the volume Bragg grating and overlaps with the optical closed-loop path; wherein the volume Bragg grating serves as a gain medium to increase the optical power of the beam; wherein a pair of counter-propagating beams is generated within the optical closed-loop path by the beam; and wherein the mirror structure and the volume Bragg grating are positioned and angled appropriately to reflect the counter-propagating beams so that they circulate around the optical closed-loop path.

[0055] Embodiment 2 includes the ring laser gyroscope according to Embodiment 1, wherein the volume Bragg grating includes rare-earth doped glass.

[0056] Embodiment 3 includes the ring laser gyroscope according to any one of Embodiments 1 to 2, wherein the volume Bragg grating includes neodymium (Nd)-doped glass, ytterbium (Yb)-doped glass, or erbium (Er)-doped glass.

[0057] Embodiment 4 includes the ring laser gyroscope according to any one of Embodiments 1 to 3, wherein the volume Bragg grating is written by direct laser scribing or by ultraviolet (UV) interference.

[0058] Embodiment 5 includes the ring laser gyroscope according to any one of Embodiments 1 to 4, the ring laser gyroscope further including a first piezoelectric device coupled to the volume Bragg grating.

[0059] Embodiment 6 includes the ring laser gyroscope according to Embodiment 5, wherein the first piezoelectric device includes lead zirconate titanate.

[0060] Embodiment 7 includes the ring laser gyroscope according to any one of Embodiments 5 to 6, wherein the first piezoelectric device is configured to provide cavity length control for an optical closed-loop path to adjust the optical power of a light beam.

[0061] Embodiment 8 includes the ring laser gyroscope according to any one of Embodiments 5 to 7, and the ring laser gyroscope further includes a second piezoelectric device coupled to the mirror structure.

[0062] Embodiment 9 includes the ring laser gyroscope according to Embodiment 8, wherein the first piezoelectric device is used to operate in a push-pull mode on the volume Bragg grating to reduce the gain grating effect while still maintaining the cavity length of the optical closed-loop path.

[0063] Embodiment 10 includes the ring laser gyroscope according to any one of Embodiments 1 to 9, wherein the mirror structure includes a metal mirror or a multi-coated dielectric mirror.

[0064] Embodiment 11 includes the ring laser gyroscope according to any one of Embodiments 1 to 10, wherein the pump laser includes a semiconductor laser.

[0065] Embodiment 12 includes the ring laser gyroscope according to any one of Embodiments 1 to 11, and further includes a photoelectric detection device, and the photoelectric detection device is optically communicated with the mirror structure acting as an optical coupler such that a part of the light beam from the optical closed-loop path is coupled and output to the photoelectric detection device.

[0066] Embodiment 13 includes the ring laser gyroscope according to any one of Embodiments 1 to 12, wherein the optical closed-loop path has a substantially triangular shape.

[0067] Embodiment 14 includes the ring laser gyroscope according to Embodiment 13, wherein the at least one mirror structure includes a pair of mirror structures respectively mounted on the optical block at the first corner and the second corner of the optical closed-loop path; and the volume Bragg grating is mounted at the third corner of the optical closed-loop path.

[0068] Embodiment 15 includes the ring laser gyroscope according to Embodiment 14, and the ring laser gyroscope further includes a piezoelectric device coupled to the volume Bragg grating.

[0069] Embodiment 16 includes the ring laser gyroscope according to Embodiment 13, wherein the mirror structure is mounted on the optical block at the first corner of the optical closed-loop path; the at least one volume Bragg grating includes a first volume Bragg grating mounted at the second corner of the optical closed-loop path and a second volume Bragg grating mounted at the third corner of the optical closed-loop path; the first pump laser is optically communicated with the first volume Bragg grating; and the second pump laser is optically communicated with the second volume Bragg grating.

[0070] Embodiment 17 includes the ring laser gyroscope of Embodiment 13, wherein the mirror structure is mounted on the optical block at the first corner of the optical closed-loop path; the at least one volume Bragg grating includes a first volume Bragg grating mounted at the second corner of the optical closed-loop path and a second volume Bragg grating mounted at the third corner of the optical closed-loop path; the first pump laser is optically communicated with the first volume Bragg grating; and wherein the ring laser gyroscope further includes: a pump mirror, the pump mirror is located in the optical block and is configured to reflect the residual light of the part of the light beam passing through the first volume Bragg grating, the residual light is reflected by the pump mirror to the second volume Bragg grating, and the second volume Bragg grating is configured to allow the residual light to pass through it for recycling during the operation of the ring laser gyroscope.

[0071] Embodiment 18 includes the ring laser gyroscope according to any one of Embodiments 1 to 12, wherein the optical closed-loop path has a substantially rectangular shape.

[0072] Embodiment 19 includes the ring laser gyroscope of Embodiment 18, wherein the at least one mirror structure includes a set of three mirror structures respectively mounted on the optical block at the first corner, the second corner and the third corner of the optical closed-loop path; and the volume Bragg grating is mounted at the fourth corner of the optical closed-loop path.

[0073] Embodiment 20 includes the ring laser gyroscope according to Embodiment 18, wherein the mirror structure is mounted on the optical block at the first corner of the optical closed-loop path; the at least one volume Bragg grating includes a first volume Bragg grating mounted at the second corner of the optical closed-loop path, a second volume Bragg grating mounted at the third corner of the optical closed-loop path and a third volume Bragg grating mounted at the fourth corner of the optical closed-loop path; the first pump laser is optically communicated with the first volume Bragg grating; and the second pump laser is optically communicated with the second volume Bragg grating; wherein a first piezoelectric device is coupled to the first volume Bragg grating, and a second piezoelectric device is coupled to the second volume Bragg grating.

[0074] The present invention may be embodied in other specific forms without departing from its essential characteristics. The embodiments are to be considered in all respects only as illustrative and not restrictive. Thus, the scope of the present invention is indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.

Claims

1. A ring laser gyroscope, comprising: An optical block that defines an optical closed-loop path; At least one mirror structure mounted on the optical block and optically communicating with the optical closed-loop path; At least one volume Bragg grating mounted on the optical block and optically communicating with the optical closed-loop path; And A first pump laser optically communicating with the volume Bragg grating, the first pump laser being configured to emit a beam at a selected angle of incidence such that the beam passes through the volume Bragg grating and overlaps with the optical closed-loop path; Wherein the volume Bragg grating serves as a gain medium to increase the optical power of the beam; Wherein a pair of counter-propagating beams are generated within the optical closed-loop path by the beam; Wherein the mirror structure and the volume Bragg grating are positioned and angled appropriately to reflect the counter-propagating beams so that they circulate around the optical closed-loop path.

2. The ring laser gyroscope according to claim 1, wherein the optical closed-loop path has a substantially triangular shape; Wherein: The at least one mirror structure includes a pair of mirror structures mounted on the optical block at a first corner and a second corner of the optical closed-loop path, respectively; and The volume Bragg grating is mounted at a third corner of the optical closed-loop path; or Wherein: The mirror structure is mounted on the optical block at a first corner of the optical closed-loop path; The at least one volume Bragg grating includes a first volume Bragg grating mounted at a second corner of the optical closed-loop path and a second volume Bragg grating mounted at a third corner of the optical closed-loop path; The first pump laser optically communicates with the first volume Bragg grating; and A second pump laser optically communicates with the second volume Bragg grating; or Wherein: The mirror structure is mounted on the optical block at a first corner of the optical closed-loop path; The at least one volume Bragg grating includes a first volume Bragg grating mounted at a second corner of the optical closed-loop path and a second volume Bragg grating mounted at a third corner of the optical closed-loop path; The first pump laser optically communicates with the first volume Bragg grating; and Wherein the ring laser gyroscope further includes: A pump mirror located within the optical block and configured to reflect residual light from a portion of the beam that passes through the first volume Bragg grating, the residual light being reflected by the pump mirror to the second volume Bragg grating, the second volume Bragg grating being configured to allow the residual light to pass therethrough for recirculation during operation of the ring laser gyroscope.

3. The ring laser gyroscope according to claim 1, wherein the optical closed-loop path has a substantially rectangular shape; Wherein: The at least one mirror structure includes a set of three mirror structures mounted on the optical block at a first corner, a second corner, and a third corner of the optical closed-loop path, respectively; and The volume Bragg grating is mounted at a fourth corner of the optical closed-loop path; or Wherein: The mirror structure is mounted on the optical block at a first corner of the optical closed-loop path; The at least one volume Bragg grating includes a first volume Bragg grating mounted at a second corner of the optical closed-loop path, a second volume Bragg grating mounted at a third corner of the optical closed-loop path, and a third volume Bragg grating mounted at a fourth corner of the optical closed-loop path; The first pump laser is optically connected to the first volume Bragg grating; and A second pump laser is optically connected to the second volume Bragg grating; wherein a first piezoelectric device is coupled to the first volume Bragg grating, and a second piezoelectric device is coupled to the second volume Bragg grating.

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