Ring waveguide-based integrated photonic optical gyroscope with gain adjustment for performance improvement

Abstract

An integrated photonic optical gyroscope fabricated on a silicon nitride (SiN) waveguide platform includes a first straight waveguide that receives incident light and outputs an output light to be coupled to a photodetector to provide an optical signal for rotation sensing. The gyroscope includes a first microresonator loop adjacent to the first straight waveguide. Light is evanescently coupled from the first straight waveguide to the first microresonator loop and experiences propagation loss while circulating as a guided beam within the first microresonator loop. The guided beam is evanescently coupled back from the first microresonator loop to the first straight waveguide to provide an optical signal for rotation sensing after optical gain is transferred to the guided beam to counteract the propagation loss. In a coupled loop configuration, the first microresonator loop acts as a loss loop while optical gain is transferred to a second microresonator loop that acts as a gain loop.

Description

Technical Field

[0001] The present disclosure relates to integrated-photonics-based optical gyroscopes. Background Art

[0002] Gyroscopes (also simply referred to as “gyros”) are devices that can sense angular velocity. Applications of gyroscopes include, but are not limited to, military, aircraft navigation, robotics, autonomous vehicles, virtual reality, augmented reality, gaming, etc. Gyroscopes can be mechanical or optical and can vary in terms of accuracy, performance, cost, and size. Since optical gyroscopes do not have any moving parts, they have an advantage over mechanical gyroscopes as they are more resistant to the effects of shock, vibration, and temperature changes than mechanical gyroscopes with moving parts. The most common optical gyroscope is the fiber optical gyroscope (FOG), which operates based on the interferometry of optical phase shifts due to the Sagnac effect (a rotation-induced phenomenon encountered in interferometry). The construction of a FOG typically involves a coil including several turns of polarization-maintaining (PM) fibers. Laser light is launched into both ends of the polarization-maintaining fiber coil such that two light beams propagate in opposite directions. If the fiber coil is moving, then the light beams propagating in opposite directions experience different optical path lengths relative to each other. By establishing an interferometry system, a small path length difference proportional to the loop area enclosed by the fiber coil turns and the angular velocity of the rotating fiber coil can be measured.

[0003] However, because the Sagnac effect is relatively weak and for high performance, FOGs are bulky and require hundreds to several kilometers of fiber (in the form of a fiber coil with several turns). An alternative to the FOG is the resonant fiber optic gyroscope (RFOG), where the resonant frequency shift due to rotation from the Sagnac effect is more prominent than in the FOG. Thus, the fiber length required in an RFOG is several orders of magnitude smaller than that in a FOG. Different from the several-turn fiber coil in a FOG, a single fiber loop is used in an RFOG and light circulates in the loop. Note that another resonant-type gyroscope, called the Ring laser gyro (RLG), is different from the RFOG and FOG in that the RLG does not have fibers and the laser beam bounces in a solid glass rather than in a fiber.

[0004] Fiber-based gyroscopes can provide very high accuracy, but at the same time, they occupy a larger area, are very expensive, and are difficult to assemble because the device is constructed based on discrete optical components that require precise alignment. Usually, manual alignment is involved, which is difficult to scale up for mass production.

[0005] The present inventor proposes to replace the fiber with a waveguide-based integrated photonics component for easy integration on a semiconductor platform at low cost, which makes mass production of gyroscopes more promising. Summary of the Invention

[0006] The following is a brief overview of the present disclosure to provide a basic understanding of some aspects of the present disclosure. This overview is not a comprehensive review of the present disclosure. It neither aims to identify key or important elements of the present disclosure nor to describe any scope of a particular specific implementation of the present disclosure or any scope of any claims. Its sole purpose is to present some concepts of the present disclosure in a simplified form as a prelude to the more detailed description presented below.

[0007] An integrated photonic optical gyroscope fabricated on a silicon nitride (SiN) waveguide platform includes a first straight waveguide that receives incident light and outputs outgoing light for coupling to a photodetector to provide an optical signal for rotation sensing. The gyroscope includes a first microresonator ring adjacent to the first straight waveguide. Light is evanescently coupled from the first straight waveguide to the first microresonator ring and experiences propagation loss while circulating as a guided beam within the first microresonator ring. The guided beam is evanescently coupled back from the first microresonator ring to the first straight waveguide to provide an optical signal for rotation sensing after optical gain is transferred to the guided beam to offset the propagation loss.

[0008] In a coupled-ring configuration, the first microresonator ring acts as a loss ring while optical gain is transferred to a second microresonator ring that acts as a gain ring.

[0009] In a coupled-ring configuration, the guided beam is evanescently coupled back from the second microresonator ring to the first microresonator ring and then evanescently coupled from the first microresonator ring to the first straight waveguide to provide an optical signal for rotation sensing.

[0010] The first microresonator ring and the second microresonator ring can be fabricated on the same physical layer or different physical layers stacked vertically on top of each other. Light is evanescently coupled between two physically separated layers.

[0011] The gyroscope may have a second straight waveguide to receive incident pump light from one or more pump light sources, where the pump light provides optical gain to offset propagation losses. At least a portion of the second microresonator ring may be implanted with erbium dopants, and the erbium dopants may be excited under pump light of a specific wavelength to provide optical gain. The pump light is coupled to the second microresonator ring from at least one side to excite the erbium dopants. Alternatively, the pump light is coupled to the second microresonator ring from the top to excite the erbium dopants. The wavelength of the pump light may be 980 nm or 1440 nm - 1480 nm, depending on the wavelength for excitation of the erbium dopants. Pump light of a suitable wavelength may be coupled to the second microresonator ring to cause stimulated Raman scattering (SRS) and / or stimulated Brillouin scattering (SBS) to provide optical gain. Description of the Drawings

[0012] The present disclosure will be more fully understood from the following detailed description given below and from the accompanying drawings of various specific embodiments of the present disclosure. Note that the dimensions shown in the figures are only for illustrative purposes and are not drawn to scale.

[0013] Figure 1A Schematic top view of a waveguide-based resonant ring in an integrated photonic optical gyroscope sensing chip.

[0014] Figure 1B Transmission electron micrograph showing a silicon nitride waveguide for constructing a loss ring and a gain ring of a gyroscope according to the present disclosure. The gain ring may be doped with erbium or other optically enhancing gain materials therein.

[0015] Figure 2A Schematic top view showing two waveguide-based resonant rings (a loss ring and a gain ring) coupled to each other in a coupled-ring integrated photonic optical gyroscope sensing chip according to an embodiment of the present disclosure.

[0016] Figure 2B Schematic diagram showing two waveguide-based resonant rings (a loss ring and a gain ring) coupled to each other in a coupled-ring integrated photonic optical gyroscope sensing chip according to another embodiment of the present disclosure, where lasers with signal wavelength and pump wavelength are emitted from both ends of the sensing chip.

[0017] Figure 3 Schematic concept of an integrated photonic optical gyroscope based on a multi-layer waveguide, where the loss ring and the gain ring are in two different layers, according to an embodiment of the present disclosure.

[0018] Figure 4A top view schematically illustrating a pump laser that is integrated from the top to locally excite erbium dopants in a portion of a gain ring located on the same layer as a loss ring, according to an embodiment of the present disclosure.

[0019] Figure 5 Schematically illustrate Figure 4 A side view of the illustrated configuration.

[0020] Figure 6 A side view schematically illustrating a pump laser that is integrated from the top to locally excite erbium dopants in a portion of a gain ring located on a different layer from a loss ring, according to an embodiment of the present disclosure.

[0021] Figure 7 Schematically illustrate the integration of a heater for changing the amount of evanescent coupling between a loss ring and a gain ring, according to an embodiment of the present disclosure. Detailed implementation

[0022] Aspects of the present disclosure are directed to a compact ultra-low-loss silicon nitride waveguide-based angular rotation sensing chip, which can be integrated with other system-level integrated photon components for optical gyroscope applications.

[0023] Figure 1A Is a schematic top view of Embodiment 100, showing a waveguide-based sensing chip 110 having input / output waveguides 115 and a waveguide-based resonator ring 130. The input / output waveguides 115 and the waveguide-based resonator ring 130 together replace the fiber coil of a FOG or the fiber loop of an RFOG. The combination of the input / output waveguides 115 and the waveguide-based resonator ring 130 is sometimes referred to as a microresonator due to its small size. An integrated photonics front-end chip (not shown) can be coupled to the waveguide-based sensing chip 110 to form an integrated photonics optical gyroscope module, which can be part of an inertial measurement unit (IMU) package. Note that the IMU can have other components in addition to the optical gyroscope module, such as an accelerometer. Thus, making the optical gyroscope module compact reduces the overall size, weight, power, and cost of the IMU. This weight reduction may be crucial for certain applications, such as lightweight unmanned aerial vehicles. The IMU can be a much-needed technology component for use in combination with more mature autonomous vehicle sensing technologies, such as LiDAR (light detection and ranging), radar, and cameras, that will be used in next-generation autonomous vehicles (land and air).

[0024] In the waveguide-based sensing chip 110 (sometimes also referred to as a "gyroscope chip"), the low-loss waveguide core can be made of silicon nitride (Si3N4, abbreviated as SiN), and the waveguide coating can be made of fused silica or an oxide.Figure 1B Shows a longitudinal cross-sectional image of a waveguide chip obtained by a transmission electron microscope (TEM), which shows a silicon nitride core surrounded by oxide coatings from the top, bottom, and both sides. This waveguide structure is also simply referred to as a SiN waveguide, and a chip containing the SiN waveguide is called a SiN waveguide chip. Note that waveguide-based components on the front-end chip (which may have an on-chip light source, such as a laser, or may direct light coupled from an off-chip light source) can be based on Si or III-V compound semiconductors or a combination thereof, and can be mode-selective, as described in the co-owned provisional patent application No. 62 / 904,443 filed on September 23, 2019 and titled "System Architecture for Silicon Photonics Optical Gyroscopes with Mode-Selective Waveguides", which has been converted to the non-provisional application No. 16 / 659,424 filed on October 21, 2019 and titled "System Architecture for Integrated Photonics Optical Gyroscopes", both of which are incorporated herein by reference in their entirety.

[0025] Alternatively, the waveguide-based components of the front-end chip can also be made of SiN in a fully integrated implementation, as described in the co-owned provisional patent application No. 62 / 934,184 filed on November 12, 2019 and titled "Multi-layer Silicon Nitride Waveguide Based Integrtaed Photonics Optical Gyroscopes".

[0026] Referring back to Figure 1A , from a light source (such as a laser, not shown) at a signal wavelength λ sThe incident guided light 124 can be coupled to the input end 120 of the waveguide 115. A portion of the incident guided light 124 is evanescently coupled to the resonant ring 130 and circulates several times as the guided light 132 within the resonant ring 130 before being coupled back to the waveguide 115 and propagating towards the output end 122 of the waveguide 115. The outgoing guided light 126 can be detected by a detector (e.g., a PID photodetector or an avalanche photodiode, not shown in the figure). The resonant ring 130 can have any geometric profile (e.g., circular, elliptical, racetrack shape, etc.). The exemplary embodiment shown in the figure shows a racetrack shape of the ring. Since in the racetrack shape, the spacing "w1" between the waveguide 115 and the resonant ring 130 can remain substantially constant for the coupling length T defined by the dashed rectangle 128, the evanescent resonant coupling can be optimized by appropriate design. It should be noted that the signal can be input from two directions, such as Figure 2B shown.

[0027] Figure 2A 2. As shown in a schematic top view of an embodiment 200, two resonant waveguide rings (a loss ring 130a and a gain ring 130b) are coupled to each other in a coupled ring integrated photonic optical gyroscope sensor chip 210, rather than as Figure 1A Only one waveguide ring is shown. Recently, it has been theoretically shown that when the loss ring and the gain ring operate under critical conditions (called the "exceptional point"), the Sagnac frequency shift of the coupled-ring integrated photonic optical gyroscope can reach 108 times that of its single-ring counterpart. Interested readers can refer to the academic journal article entitled "Loss-Gain Coupled Ring Resonator Gyroscope" written by Matthew J. Grant and Michael JFDigonnet and published in Proceedings of SPIE 10934, Optical, Opto-Atomic and Entanglement-Enhanced Precision Metrology (March 4, 2019). This article also shows simulation results, which demonstrate that the maximum rotational sensitivity of the coupled-ring gyroscope structure is not achieved at the exceptional point, but at the optimal value of the inter-ring coupling far away from the exceptional point. Therefore, controlling the loss and gain in the two waveguide rings is crucial to achieving optimal inter-ring coupling and then achieving the desired rotational sensitivity.

[0028] The present inventors propose various embodiments of coupled ring gyroscopes based on loss rings and gain rings of silicon nitride waveguides. Note that the loss rings 130a and 130b do not have to be the same size. Figure 4Embodiments showing the shapes of different rings are presented. The shapes of the rings are designed to optimize the coupling between two rings separated by a lateral distance “w2” within the dashed region 128b, as well as to optimize the coupling between the lossy ring 130a and the waveguide 115 separated by a lateral distance “w1” within the dashed region 128a, and the coupling between the gain ring 130b and the waveguide 215 separated by a lateral distance “w3” within the dashed region 128c. The direction of the guided beam 132a within the lossy ring 130a is opposite to the direction of the guided beam 132b within the gain ring 130b. To introduce optical gain into the guided beam 132b, pump laser light 224 of the target wavelength can be emitted into the input end 220 of the waveguide 215. The wavelength of the pump laser light 224 can be selected such that the wavelength of the amplified light coupled from the waveguide 215 to the gain ring 130b is equal to the signal wavelength λ of the laser emitted at the input end 120 of the waveguide 115 s . The signal wavelength λ s can be 1550 nm or some other wavelength optimized for waveguide loss by design. The wavelength of the amplified light can be a Raman-shifted or Brillouin-shifted emission wavelength or its harmonic, depending on whether the pump laser is used to cause Stimulated Raman Scattering (SRS) or Stimulated Brillouin Scattering (SBS) as the gain mechanism. In certain embodiments of the erbium-doped gain ring 130b (similar to an erbium doped fiber amplifier (EDFA)), the pump laser wavelength does not need to match the signal wavelength λ s , but needs to excite erbium-doped ions, for example, at -980 nm. (Note that the exact wavelength required to excite erbium depends on the type of erbium used.) Note that other typical wavelengths for pumping may be in the range of 1440 nm - 1480 nm. This wavelength range may be more practical for side pumping (as shown in Figure 2A and Figure 2B ) rather than top pumping (as shown in Figures 4 to 6 ). In another embodiment, the pump laser for causing SRS or SBS and the 980 nm pump laser for exciting erbium-doped ions can be used together to further enhance the signal and system performance. This concept is further elaborated in reference to the following Figure 4 and Figure 5 . Since the waveguide dimensions in the gain ring 130b may not be optimized to guide the 980 nm wavelength with low loss, in certain embodiments, more than one pump laser can be coupled at the waveguide input end 220, that is, one 980 nm pump laser, and another generating a wavelength equal to the signal wavelength λ sA pump laser for amplified light. The output end 222 of the waveguide 215 can be blocked, or the outgoing light 226 can be directed to a detector to measure how much optical power is coupled into the gain loop 130b.

[0029] Figure 2B Another embodiment similar to Figure 2A is shown, but in this embodiment, the lasers for the signal wavelength λ s and the pump wavelength λ p can be input from both sides of the chip 210. The incident guided light with wavelength λ s can come from the same laser source or the front-end chip, and this light is split into two light beams (124 and 127) by a beam splitter. In addition, the light from a pump laser with a wavelength λ p optimized for SBS or SRS can also pump as light beams 224 and 227 from both sides of the loop to provide double gain in the system and ensure that the same amplification is seen for the signal passing through the gain loop in both directions. Alternatively, the light beam 224 can have a wavelength that excites erbium-doped ions (which will be described below), and the light beam 227 can have a wavelength suitable for causing SRS or SBS. Generally speaking, pumping from both sides of the loop (i.e., double pumping) allows the laser signal to rotate through the loop in both directions, similar to a standard FOG (where light is emitted from two directions in a fiber coil). This is why a pump wavelength of 1440 nm - 1480 nm is convenient for producing the desired results. Then, these two circulating light beams will see the same temperature effect, the same path length, and other system differences. However, the resonance shift will be different depending on the direction of system rotation. This can cancel out other effects and ensure that the signal being measured comes from the Sagnac effect.

[0030] Note that Figure 2A and Figure 2B illustrate two loops (a loss loop and a gain loop) fabricated on the same layer of the chip 210, and the evanescent coupling from loop to loop occurs laterally in the same transverse plane. However, in an alternative embodiment, when the loss loop and the gain loop are fabricated in two separate layers, the evanescent coupling from loop to loop can occur vertically in the longitudinal plane (as shown in the example of Figure 6 ).

[0031] Figure 3Embodiment 300 is shown, which shows a first layer 310a having a loss ring 130a and a second layer 310b having a gain ring 130b. For purposes of illustration, the two rings may be separated by an amount "w2" (where "w2" may be zero) in the transverse direction (x-direction), and the projection of the loss ring 130a is shown as a dashed outline 330a on layer 310b. Evanescent vertical coupling of the guiding beams 132a and 132b occurs between the portion of the loss ring 130a within the dashed outline 328a on layer 310a and the portion of the gain ring 130b within the dashed outline 328b on layer 310b. Note that in some embodiments, the gain ring may be on the top layer and the loss ring on the bottom layer.

[0032] Figure 4 and Figure 5 Embodiment 400 is shown, where the waveguide core region of the gain ring 130b is implanted with erbium dopant ions, which may be excited by a suitable pump laser at a wavelength of 980 nm or 1440 nm. Specifically, Figure 4 A top view of the sensing chip 410 (similar to the sensing chip 210 in FIG. 2) is shown, and [[ID=�]] Figure 5 A portion of the longitudinal cross-section of the chip 410 along the Figure 4 cutting line AA' shown in Figure 4 is shown. Note that Figure 4 has many components similar to those in FIG. 2, but instead of using an additional waveguide 215 to emit pump laser light from the edge as in the case of the sensing chip 210, the pump laser 460 is coupled from the top of the sensing chip 410. The portion of the gain ring 130b directly below the pump laser 460 receives the laser light 524 ( Figure 5 not shown in

[0033] Figure 5 but shown in

[0034] ), which excites the erbium dopant ions 485 (represented by stars) around the SiN core 570 of the waveguide and amplifies the beam 132b circulating in the gain ring 130b.

[0033] Figure 5 The depth of the implanted erbium dopant is shown (primarily confined within the implantation region 580, which is not a separate material layer but represents the portion of the waveguide plating with erbium ions), and this depth is determined by the depth at which the waveguide core 570 of the gain ring 132b resides from the top surface of the chip 410. A mirror 562 may be fabricated on top of the pump laser 460 such that light 524 at a wavelength of 980 nm is pumped into the chip 410 to excite the erbium dopant ions in the implanted layer 580. Since most of the optical mode (shown by the dashed ellipse 565) is outside the SiN core 570, the excited erbium ions 585 within the spatial optical mode are able to optically amplify the guiding beam 132b in the gain ring 130b.

[0034] In some embodiments, optical gain is introduced only at a portion of the gain loop 130b that is directly under the pump laser and away from the loop-to-loop coupling region 128b, as Figure 4 shown. In some other embodiments, the entire gain loop 130b may be under the pump laser 460.

[0035] In the case of a multi-layer structure, the gain loop may be on the top and the loss loop may be on the bottom. For example, in Figure 6 the illustrated embodiment 600, a longitudinal cross-section of the sensing chip is shown, where the top layer 610b has a gain loop 130b (i.e., the SiN waveguide cross-sections 570a and 570b belong to the gain loop 130b), while the bottom layer 610a has a loss loop 130a (i.e., the SiN waveguide cross-sections 570c and 570d belong to the loss loop 130a). Note that the waveguide cross-sections 570b and 570c may be aligned with respect to each other to obtain optimal vertical coupling between the gain loop and the loss loop. For example, "w2" may be zero or even negative. The coupling efficiency also depends on the vertical spacing "h".

[0036] Figure 7 Embodiment 700 is shown, where the heater 780 is made to cover the coupling region 128b on the top surface of the sensing chip 410 (whose longitudinal cross-section is shown in the figure). This particular embodiment shows a single-layer structure similar to Figure 4 where the gain loop (waveguides 570a and 570b) and the loss loop (waveguides 570c and 570d) are both in the same layer. The gain loop can be pumped from the top or the side for optical amplification at the signal wavelength. By controlling the power of the heater 780, the amount of coupling between the gain loop and the loss loop can be controlled. Additionally, the same concept of the metal heater can be deployed on other loops above regions W1 and W3 to adjust the amount of coupling in and out of the loops.

[0037] Note that although the pump laser is shown in the figures as being attached or bonded as a die on the top of the layer having the gain loop, in some embodiments, the pump laser may be formed or monolithically integrated into the rest of the sensing chip as a third top layer or edge-coupled.

[0038] In the foregoing specification, specific embodiments of the present disclosure have been described with reference to their particular exemplary embodiments. It will be apparent that various modifications can be made thereto without departing from the broader spirit and scope of the specific embodiments of the present disclosure set forth in the claims below. Accordingly, the specification and drawings are to be interpreted in an illustrative rather than a restrictive sense. Additionally, directional terms, such as "top", "bottom", etc., do not limit the scope of the present disclosure to any fixed orientation, but rather encompass various arrangements and combinations of orientations.

Claims

1. An integrated photonic optical gyroscope fabricated on a silicon nitride (SiN) waveguide platform, comprising: A first straight waveguide that receives incident light from one or more light sources and outputs an outgoing light to be coupled to a photodetector to provide an optical signal for rotation sensing; A first microresonator ring adjacent to a portion of the first straight waveguide, wherein light is evanescently coupled from the portion of the first straight waveguide to the first microresonator ring and experiences propagation loss as a guided beam circulates within the first microresonator ring; A second microresonator ring adjacent to a portion of the first microresonator ring, wherein the guided beam is evanescently coupled from the portion of the first microresonator ring to a portion of the second microresonator ring and experiences optical gain to offset the propagation loss within the first microresonator ring and the second microresonator ring; And A second straight waveguide for receiving incident pump light from one or more pump light sources, wherein a portion of the second straight waveguide is adjacent to the second microresonator ring, and wherein the pump light provides the optical gain to offset the propagation loss, Wherein after the optical gain is transferred to the guided beam to offset the propagation loss, the guided beam is evanescently coupled back from the first microresonator ring to the portion of the first straight waveguide to provide the optical signal for rotation sensing, Wherein the pump light is coupled from the second straight waveguide to the second microresonator ring, and the pump light is emitted into the second straight waveguide from both ends.

2. The integrated photonic optical gyroscope according to claim 1, wherein the one or more light sources are located at one end or both ends of the first straight waveguide.

3. The integrated photonic optical gyroscope according to claim 1, wherein the guided beam is evanescently coupled back from the second microresonator ring to the first microresonator ring, and is evanescently coupled from the first microresonator ring to the portion of the first straight waveguide to provide the optical signal for rotation sensing.

4. The integrated photonic optical gyroscope according to claim 1, wherein the first microresonator ring and the second microresonator ring have the same shape and size.

5. The integrated photonic optical gyroscope according to claim 1, wherein the shape, size, or both the shape and size of the first microresonator ring are different from the shape, size, or both the shape and size of the second microresonator ring.

6. The integrated photonic optical gyroscope according to claim 1, wherein the first microresonator ring and the second microresonator ring are fabricated on different physical layers stacked vertically on top of each other, and wherein light is evanescently coupled between the two vertically separated physical layers.

7. The integrated photonic optical gyroscope according to claim 6, wherein the first microresonator ring and the second microresonator ring are laterally offset with respect to each other.

8. The integrated photonic optical gyroscope according to claim 1, wherein at least a portion of the second microresonator ring is implanted with erbium dopants, and the erbium dopants can be excited under pump light of a specific wavelength to provide the optical gain.

9. The integrated photonic optical gyroscope according to claim 8, wherein a pump light source is disposed on top of the at least a portion of the second microresonator ring, and the portion is implanted with the erbium dopants.

10. The integrated photonic optical gyroscope according to claim 9, wherein a mirror is formed on top of the pump light source to enhance the vertical injection of the pump light toward the erbium dopants.

11. The integrated photonic optical gyroscope according to claim 9, wherein the second microresonator ring is formed on a top vertical layer adjacent to the pump light source, and the first microresonator ring is formed on a bottom vertical layer below the top vertical layer.

12. The integrated photonic optical gyroscope according to claim 11, wherein a heater is formed on top of the top vertical layer to adjust the amount of evanescent coupling between the second microresonator ring and the first microresonator ring.

13. The integrated photonic optical gyroscope according to claim 1, wherein the first and second microresonator rings are formed on a common physical layer, and a heater is formed on top of the common physical layer to adjust the amount of evanescent coupling between the second microresonator ring and the first microresonator ring.

14. The integrated photonic optical gyroscope according to claim 1, wherein pump light of a suitable wavelength is coupled into the second microresonator ring to initiate stimulated Raman scattering (SRS) to provide the optical gain.

15. The integrated photonic optical gyroscope according to claim 1, wherein the pump light of a suitable wavelength is coupled into the second microresonator ring to initiate stimulated Brillouin scattering (SBS) to provide the optical gain.

16. The integrated photonic optical gyroscope according to claim 1, wherein a first pump light is coupled into the second microresonator ring from at least one side, and a second pump light is coupled into the second microresonator ring from the top.

17. The integrated photonic optical gyroscope according to claim 1, wherein at least a portion of the second microresonator ring is implanted with erbium dopants, and the erbium dopants can be excited under pump light of a specific wavelength to provide the optical gain.

18. A coupled-ring integrated photonic optical gyroscope fabricated on a silicon nitride (SiN) waveguide platform, comprising: A first straight waveguide that receives incident light from one or more light sources and outputs output light to be coupled to a photodetector to provide an optical signal for rotation sensing; A first microresonator ring adjacent to a portion of the first straight waveguide, wherein light is evanescently coupled from the portion of the first straight waveguide into the first microresonator ring and experiences propagation loss while circulating as a guided beam within the first microresonator ring; A second microresonator loop, the second microresonator loop being adjacent to a portion of the first microresonator loop, wherein the guiding beam evanescently couples from the portion of the first microresonator loop to a portion of the second microresonator loop and experiences optical gain to counteract propagation losses within the first microresonator loop and the second microresonator loop; and A second straight waveguide for receiving incident pump light from one or more pump light sources, wherein a portion of the second straight waveguide is adjacent to the second microresonator loop, and wherein the pump light provides the optical gain to counteract the propagation losses, wherein the pump light couples from the second straight waveguide to the second microresonator loop, and the pump light is emitted into the second straight waveguide from both ends.

19. The coupled-loop integrated photonic optical gyroscope according to claim 18, wherein the guiding beam evanescently couples back from the second microresonator loop to the first microresonator loop, and evanescently couples from the first microresonator loop to the portion of the first straight waveguide to provide the optical signal for rotation sensing.

20. The coupled-loop integrated photonic optical gyroscope according to claim 18, wherein the first microresonator loop and the second microresonator loop are fabricated on different physical layers stacked vertically on top of each other, and wherein light evanescently couples between the two physically separated layers.

21. The coupled-loop integrated photonic optical gyroscope according to claim 19, wherein at least a portion of the second microresonator loop is implanted with erbium dopants, and the erbium dopants can be excited under pump light of a specific wavelength to provide the optical gain.

22. The coupled-loop integrated photonic optical gyroscope according to claim 21, wherein the pump light couples to the second microresonator loop from at least one side to excite the erbium dopants.

23. The coupled-loop integrated photonic optical gyroscope according to claim 21, wherein the pump light couples to the second microresonator loop from the top to excite the erbium dopants.

24. The coupled-loop integrated photonic optical gyroscope according to claim 21, wherein the wavelength of the pump light depends on the excitation wavelength of the erbium dopants.

25. The coupled-loop integrated photonic optical gyroscope according to claim 18, wherein pump light of a suitable wavelength is coupled to the second microresonator loop to initiate stimulated Raman scattering (SRS) to provide the optical gain.

26. The coupled-loop integrated photonic optical gyroscope according to claim 18, wherein pump light of a suitable wavelength is coupled to the second microresonator loop to initiate stimulated Brillouin scattering (SBS) to provide the optical gain.

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