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

Abstract

An integrated photonics optical gyroscope fabricated on a silicon nitride (SiN) waveguide platform includes a first straight waveguide that receives incident light and outputs output light that is coupled to a photodetector to provide an optical signal for rotation sensing. The gyroscope includes a first microresonator ring proximate to the first straight waveguide. Light evanescently couples from the first straight waveguide into the first microresonator ring and experiences propagation losses as it circulates as a guided beam within the first microresonator ring. Optical gain is imparted to the guided beam to counter the propagation losses, after which the guided beam evanescently couples from the first microresonator ring back into the first straight waveguide to provide an optical signal for rotation sensing. In a coupled-ring configuration, the first microresonator ring acts as a loss ring, and optical gain is imparted to a second microresonator ring that acts as a gain ring.

Description

[Technical field]

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

[0002] A gyroscope (also called "gyro" for short) is a device 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 accuracy, performance, cost, and size. Optical gyroscopes have advantages over mechanical gyroscopes because they have no moving parts and can withstand the effects of shock, vibration, and temperature fluctuations better than mechanical gyroscopes that have moving parts. The most common optical gyroscope is the fiber optic gyroscope (FOG), which operates based on interferometric measurement of optical phase shift due to the Sagnac effect (a phenomenon occurring in rotation-induced interferometry). FOG constructions typically include a coil with several turns of polarization-maintaining (PM) fiber. Laser light is launched into both ends of the PM fiber coil so that the two light beams travel in opposite directions. When the fiber coil moves, the light beams traveling in opposite directions experience different optical path lengths relative to each other. The interferometer system can be set up to measure small path length differences that are proportional to the area of ​​the loop enclosed by the windings of the fiber coil and the angular velocity of the rotating fiber coil.

[0003] However, the Sagnac effect is relatively weak, and hundreds to thousands of meters of fiber (in the form of a fiber coil with several turns) are required to obtain high performance, making FOGs bulky. An alternative form of FOG is the resonant fiber optic gyroscope (RFOG), in which the rotation-induced resonant frequency shift due to the Sagnac effect is much more pronounced than in FOGs. As a result, the required length of fiber in an RFOG is several orders of magnitude smaller than in a FOG. Instead of a few turns of fiber coil in a FOG, a single loop of fiber is used in an RFOG, in which the light circulates. It is noted that another resonant type gyroscope, called a ring laser gyro (RLG), differs from RFOGs and FOGs in the sense that an RLG does not have fiber, and instead of a fiber, a laser beam bounces in a solid piece of glass.

[0004] Fiber-based gyroscopes can achieve very high accuracy, but at the same time have a larger footprint, are very expensive, and are difficult to assemble due to the devices being built on separate optical components that must be precisely aligned, often involving manual alignment that is difficult to scale for mass production.

[0005] The inventors propose to replace the fiber with waveguide-based integrated photonics components for cost-effective and easy integration on a semiconductor platform that is much more promising for mass production of gyroscopes. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Nonprovisional Patent Application No. 16 / 659,424 [Patent Document 2] Provisional Patent Application No. 62 / 904,443 [Patent Document 3] Provisional Patent Application No. 62 / 934,184 [Non-patent literature]

[0007] [Non-Patent Document 1] "Loss-Gain Coupled Ring Resonator Gyroscope," published in Proceedings of SPIE 10934, Optical, Opto-Atomic and Entanglement-Enhanced Precision Metrology (4 March 2019), edited by Matthew J. Grant and Michael J.F. Digonnet Summary of the Invention [Means for solving the problem]

[0008] The following is a brief summary of the disclosure to provide a basic understanding of some aspects of the disclosure. This summary is not an extensive overview of the disclosure. It is not intended to identify key or critical elements of the disclosure or to describe any scope of particular implementations of the disclosure or any scope of the claims. The sole purpose of this summary is to present some concepts of the disclosure in a simplified form as a prelude to the more detailed description presented later.

[0009] An integrated photonics optical gyroscope fabricated on a silicon nitride (SiN) waveguide platform includes a first straight waveguide that receives incoming light and outputs outgoing light that is coupled to a photodetector to provide an optical signal for rotation sensing. The gyroscope includes a first microresonator ring proximate to the first straight waveguide. Light evanescently couples from the first straight waveguide into the first microresonator ring and experiences propagation losses while circulating as a guided beam within the first microresonator ring. The guided beam evanescently couples back from the first microresonator ring into the first straight waveguide after optical gain is applied to the guided beam to combat the propagation losses, providing an optical signal for rotation sensing.

[0010] In the coupled-ring configuration, a first microresonator ring acts as a loss ring, and optical gain is imparted to a second microresonator ring, which acts as a gain ring.

[0011] In the coupled-ring configuration, the guided beam evanescently couples from the second microresonator ring to the first microresonator ring and from the first microresonator ring back to the first straight waveguide to provide an optical signal for rotation sensing.

[0012] The first and second microresonator rings can be fabricated on the same physical layer or on different physical layers stacked vertically on top of each other, and light evanescently couples between the two vertically separated physical layers.

[0013] The gyroscope can have a second straight waveguide that receives incident pump light from one or more pump light sources, where the pump light provides optical gain to counter propagation losses. At least a portion of the second microresonator ring can be infused with an erbium dopant that can be excited with a particular wavelength of the pump light to provide optical gain. The pump light is coupled into the second microresonator ring from at least one side to excite the erbium dopant. Alternatively, the pump light is coupled into the second microresonator ring from above to excite the erbium dopant. The pump light can be at a wavelength of 980 nm or 1440-1480 nm, depending on the wavelength of the excitation for the erbium dopant. Pump light of a suitable wavelength can be coupled into the second microresonator ring to induce stimulated Raman scattering (SRS) and / or stimulated Brillouin scattering (SBS) to provide optical gain.

[0014] The present disclosure will become more fully understood from the detailed description given below and the accompanying drawings of various implementations of the present disclosure. It should be noted that the dimensions shown in the figures are for illustrative purposes only and are not drawn to scale. [Brief description of the drawings]

[0015] [Figure 1A] FIG. 1 is a schematic top view illustrating a waveguide-based resonating ring in an integrated photonics optical gyroscope sensing chip. [Figure 1B] 1 is a transmission electron micrograph showing silicon nitride waveguides used to construct the loss and gain rings of a gyroscope according to the present disclosure. The gain rings can have erbium doped in them or other optically enhanced gain materials. [Figure 2A] FIG. 2 is a schematic top view illustrating two waveguide-based resonant rings (one loss ring and one gain ring) coupled to each other in a coupled-ring integrated photonics optical gyroscope sensing chip according to an embodiment of the present disclosure. [Figure 2B] FIG. 13 is a schematic diagram illustrating two waveguide-based resonant rings (one loss ring and one gain ring) coupled to each other in a coupled-ring integrated photonics optical gyroscope sensing chip according to another embodiment of the present disclosure, where laser light having a signal wavelength and a pump wavelength is launched from both ends of the sensing chip. [Diagram 3] FIG. 1 illustrates a concept centered on fabricating a multi-layer waveguide-based integrated photonics optical gyroscope according to an embodiment of the present disclosure, where the loss ring and the gain ring are in two different layers. [Figure 4] FIG. 2 is a top view diagram that diagrammatically illustrates a pump laser integrated from above to locally induce erbium dopants in a portion of a gain ring that is located on the same layer as a loss ring, in accordance with an embodiment of the present disclosure. [Diagram 5] FIG. 5 is a side view that diagrammatically illustrates the configuration shown in FIG. 4. [Figure 6] FIG. 2 is a side view diagram that diagrammatically illustrates a pump laser integrated from above to locally induce erbium dopants in a portion of a gain ring that is located on a different layer than a loss ring, in accordance with an embodiment of the present disclosure. [Figure 7]1A-1C are diagrams that illustrate schematics of the integration of heaters to vary the amount of evanescent coupling between the loss ring and the gain ring, in accordance with an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Aspects of the present disclosure are directed to a compact, ultra-low loss silicon nitride waveguide-based angular rotation sensing chip that can be integrated with other system-level integrated photonics components for optical gyroscope applications.

[0017] FIG. 1A is a schematic top view of an embodiment 100 showing a waveguide-based sensing chip 110 with input / output waveguides 115 and a waveguide-based resonating ring 130 that collectively replaces 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 resonating ring 130 may be referred to as a microresonator due to its small size. An integrated photonics front-end chip (not shown) may be coupled to the waveguide-based sensing chip 110 to build an integrated photonics optical gyroscope module that may be part of an inertial measurement unit (IMU) package. It is noted that the IMU may have other components such as an accelerometer in addition to the optical gyroscope module. Thus, by miniaturizing the optical gyroscope module, the overall size, weight, power, and cost of the IMU are reduced. This reduction in weight may be important for certain applications, for example, lightweight unmanned aerial vehicles. IMUs may be a much needed technology component to work in conjunction with more established sensing technologies for autonomous vehicles, such as LiDAR (light detection and ranging), radar, and cameras, that will be used in future generations of autonomous vehicles (both ground and air).

[0018] In the waveguide-based sensing chip 110 (sometimes called a "gyro chip"), a low-loss waveguide core is fabricated using silicon nitride (Si 3 N 4, simply referred to as SiN) and the waveguide cladding may be made of fused silica or oxide. Figure 1B shows a longitudinal cross-sectional image of a waveguide chip obtained by transmission electron microscopy (TEM), showing a silicon nitride core surrounded by oxide cladding from above, below, and both sides. This waveguide structure is also simply referred to as a SiN waveguide, and a chip containing a SiN waveguide is called a SiN waveguide chip. It should be noted that, as described in commonly owned prior application U.S. Patent Publication 2, entitled "System Architecture for Silicon Photonics Optical Gyroscopes with Mode-Selective Waveguides," filed on September 23, 2019, amended to U.S. Patent Publication 1, entitled "System Architecture for Integrated Photonics Optical Gyroscopes," filed on October 21, 2019, both of which are incorporated by reference in their entireties herein, the waveguide-based components on the front-end chip (which may have an on-chip light source such as a laser or may guide light coupled from an off-chip light source) may be based on Si or III-V compound semiconductors or a combination thereof and may be mode-selective.

[0019] Alternatively, the waveguide-based components of the front-end chip may also be made of SiN in an all-integrated embodiment, as described in commonly owned U.S. Patent Application Publication No. 2019 / 0133634, entitled “Multi-layer Silicon Nitride Waveguide Based Integrated Photonics Optical Gyroscopes,” filed November 12, 2019.

[0020] Referring back to FIG. 1A, the signal wavelength λ sAn incident guided light 124 from a light source (such as a laser, not shown) can be coupled to the input end 120 of the waveguide 115 at . A portion of the incident guided light 124 is evanescently coupled into the resonant ring 130, circulates within the resonant ring 130 several times as guided light 132, and then couples back into the waveguide 115 to propagate toward 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). The resonant ring 130 can have any geometric shape (e.g., a circle, an oval, a racetrack shape, etc.). The illustrative example shown in the figure shows a racetrack shape for the ring. In the racetrack shape, the separation "w1" between the waveguide 115 and the resonant ring 130 can be kept nearly constant for a coupling length "l" bounded by the dashed rectangle 128, so that by appropriate design, the evanescent resonant coupling can be optimized. Note that signals can be input in both directions, as shown in FIG. 2B.

[0021] 2A illustrates a schematic top view of an embodiment 200 in which two resonant waveguide rings (one loss ring 130a and one gain ring 130b) are coupled to each other in a coupled-ring integrated photonics optical gyroscope sensing chip 210, instead of just one waveguide ring as shown in FIG 1A. Recently, it has been reported that when the loss and gain rings are operated at a critical operating condition known as the "exclusion point", the Sagnac frequency shift of a coupled-ring integrated photonics optical gyroscope can be up to 10 times that of its single-ring counterpart. 8 It has been theoretically shown that the coupling loss can be doubled. The interested reader is referred to the journal article "Coupled-ring gyroscope design with a gyro-coupled ring with a gyro-coupled ring," IEEE Transactions on Gyro-Sensing, Vol. 13, No. 1, pp. 1171-1175, 2002. This document also shows that simulation results indicate that the highest rotation sensitivity of the coupled-ring gyroscope configuration is not achieved at the exclusion point, but at an optimal value of inter-ring coupling, away from the exclusion point. Thus, controlling the loss and gain in the two waveguide rings is critical to achieving optimal inter-ring coupling and, in turn, the desired rotation sensitivity.

[0022] The inventors propose various embodiments of coupled ring gyroscopes based on silicon nitride waveguide-based loss rings and gain rings. It should be noted that the dimensions of the loss rings 130a and 130b do not need to be identical. Examples of non-identical shapes are shown in FIG. 4. The ring shapes are designed to optimize the coupling between the two rings separated by the lateral distance "w2" in the dotted area 128b, as well as the coupling between the loss ring 130a and the waveguide 115 separated by the lateral distance "w1" in the dotted area 128a, and the coupling between the gain ring 130b and the waveguide 215 separated by the lateral distance "w3" in the dotted area 128c. The direction of the guided light beam 132a in the loss ring 130a is opposite to the direction of the guided light beam 132b in the gain ring 130b. To provide optical gain to guided light beam 132b, pump laser light 224 can be launched into input end 220 of waveguide 215 at a target wavelength. The wavelength of pump laser light 224 is determined so that the wavelength of the amplified light coupled from waveguide 215 to gain ring 130b is equal to or greater than the signal wavelength λ of the laser light launched at input end 120 of waveguide 115. s The signal wavelength λ can be chosen to be equal to s may be 1550 nm, or some other wavelength for which the waveguide losses are optimized by design. Depending on whether the pump laser is used to induce stimulated Raman scattering (SRS) or stimulated Brillouin scattering (SBS) as the gain mechanism, the wavelength of the amplified light may be the Raman-shifted or Brillouin-shifted emission wavelength or a harmonic thereof. In certain embodiments where the gain ring 130b is doped with erbium (as in an erbium-doped fiber amplifier (EDFA)), the pump laser wavelength is 1550 nm, or some other wavelength for which the waveguide losses are optimized by design. s, but need not coincide with the wavelength of the gain ring 130b to guide the erbium dopant ions at, for example, about 980 nm. (Note that the exact wavelength required to guide the erbium depends on the type of erbium used.) Note that other typical wavelengths for pumping may be in the range of 1440-1480 nm. Wavelengths in that range may be more practical with pumping from the side (as shown in FIGS. 2A and 2B) rather than pumping from above (as shown in FIGS. 4-6). In another embodiment, both the pump laser used to induce SRS or SBS and a 980 nm pump laser for exciting the erbium dopant ions may be used together to further improve signal and system performance. This concept is further elaborated with respect to FIGS. 4 and 5 below. In certain embodiments, one pump laser is 980 nm and another pump laser is at the signal wavelength λ because the dimensions of the waveguide in the gain ring 130b may not be optimized to guide the 980 nm wavelength with low loss. s More than one pump laser generating a wavelength of amplified light equal to can be coupled to the waveguide input end 220. The output end 222 of the waveguide 215 can be blocked, or the output light 226 can be directed to a detector to measure how much optical power is coupled into the gain ring 130b.

[0023] FIG. 2B shows another embodiment similar to FIG. 2A, but in this embodiment, the signal wavelength λ s and pump wavelength λ pLaser light for both can be input from both sides of the chip 210. The input guided light with wavelength λs, which is split into two beams (124 and 127) via a splitter, can come from the same laser source or front-end chip. In addition, light from a pump laser with wavelength λp optimized for either SBS or SRS can also be pumped from both sides of the ring as beams 224 and 227, allowing the gain in the system to be doubled and also ensuring that the signals in both directions passing through the gain ring are of the same amplitude. Alternatively, beam 224 can have a wavelength that excites erbium dopant ions (as described below) and beam 227 can have a wavelength suitable for inducing SRS or SBS. In general, pumping from both sides of the ring (i.e., double pumping) allows the laser signal to rotate through the ring in both directions, similar to a standard FOG (where light is injected from both directions in the fiber coil). This is why pump wavelengths of 1440-1480 nm are convenient for achieving the desired results. Both of these circulating beams will experience the same temperature effects, the same path length, and other system differences, but the resonance shift will be different depending on which way the system rotates, allowing us to cancel out other effects and ensure that the signal we measure is due to the Sagnac effect.

[0024] 2A and 2B illustrate two rings (a loss ring and a gain ring) fabricated on the same layer of chip 210, and it should be noted that the ring-to-ring evanescent coupling occurs laterally in the same horizontal plane. However, in alternative embodiments, when the loss and gain rings are fabricated on two separate layers, the ring-to-ring evanescent coupling may occur vertically in the longitudinal plane (as shown for example in FIG. 6).

[0025] FIG. 3 illustrates an embodiment 300 showing a first layer 310a with a loss ring 130a and a second layer 310b with a gain ring 130b. To illustrate that the two rings can be separated along the lateral direction (x-direction) by an amount "w2" (where "w2" can be zero), a projection of the loss ring 130a is shown in the form of a dotted outline 330a on the layer 310b. Vertical evanescent coupling of the guided light beams 132a and 132b occurs between a portion of the loss ring 130a within a dotted outline 328a on the layer 310a and a portion of the gain ring 130b within a dotted outline 328b on the layer 310b. Note that in some embodiments, the gain ring may be on the upper layer while the loss ring is on the lower layer.

[0026] Figures 4 and 5 show an embodiment 400 in which the waveguide core region of the gain ring 130b is implanted with erbium dopant ions that can be stimulated with the preferred pump laser wavelengths of 980 nm or 1440 nm. Specifically, Figure 4 shows a top view of a sensing chip 410 (similar to sensing chip 210 of Figure 2), and Figure 5 shows a portion of a longitudinal cross section of the chip 410 along section line AA' shown in Figure 4. Note that Figure 4 has many similar components to Figure 2, but instead of using an additional waveguide 215 to launch the pump laser light from the end as in the case of sensing chip 210, a pump laser 460 is coupled from the top of the sensing chip 410. The portion of gain ring 130b directly below pump laser 460 receives laser light 524 (not shown in FIG. 4, but illustrated in FIG. 5) that stimulates erbium dopant ions 485 (the star shape indicates stimulated erbium ions) around the SiN core 570 of the waveguide and amplifies light beam 132b circulating in gain ring 130b.

[0027] 5 shows, the depth to which the erbium dopant is implanted (which is mostly confined to the implanted region 580, which is not a separate material layer but represents a portion of the waveguide cladding with erbium ions) is determined by the depth to which the waveguide core 570 of the gain ring 132b resides from the top surface of the chip 410. A mirror 562 can be fabricated above the pump laser 460 so that light 524 at a wavelength of 980 nm is pumped into the chip 410, stimulating the erbium dopant ions in the implanted region 580. Because most of the optical mode (represented by the dotted oval 565) is outside the SiN core 570, the spatially induced erbium ions 585 in the optical mode can provide optical amplification for the guided beam 132b in the gain ring 130b.

[0028] In some embodiments, optical gain is provided only in the portion of the gain ring 130b that is directly under the pump laser and away from the ring-to-ring coupling region 128b, as shown in Figure 4. In certain other embodiments, the entire gain ring 130b may be under the pump laser 460.

[0029] In the case of a multi-layer configuration, the gain ring may be at the top and the loss ring may be at the bottom. For example, in the embodiment 600 shown in FIG. 6, a longitudinal cross section of a sensing chip is shown, where the top layer 610b has the gain ring 130b (i.e., the SiN waveguide cross sections 570a and 570b belong to the gain ring 130b) and the bottom layer 610a has the loss ring 130a (i.e., the SiN waveguide cross sections 570c and 570d belong to the loss ring 130a). It should be noted that the waveguide cross sections 570b and 570c may be aligned with respect to each other to achieve optimal vertical coupling between the gain ring and the loss ring. For example, "w2" may be zero or even a negative number. The coupling efficiency also depends on the vertical spacing "h".

[0030] FIG. 7 shows an embodiment 700 in which a heater 780 is fabricated covering the coupling region 128b on the top surface of the sensing chip 410 (its longitudinal cross section is shown in the figure). This particular example shows a single layer configuration as in FIG. 4, where both the gain ring (waveguides 570a and 570b) and the loss ring (waveguides 570c and 570d) are in the same layer. The gain ring can be pumped from the top or from the side for optical amplification at the signal wavelength. The power of the heater 780 can be controlled to control the amount of coupling between the gain ring and the loss ring. In addition, metal heaters of the same concept can be deployed on the other rings above the regions W1 and W3 to adjust the amount of coupling to and from the rings.

[0031] In the figures, the pump laser is shown attached to the die or bonded onto the layer with the gain ring, but in certain embodiments the pump laser can be grown as the top third layer or end bonded or monolithically integrated with the rest of the detector chip.

[0032] In the above specification, the implementation of the present disclosure has been described with reference to specific exemplary implementations thereof. It is apparent that various modifications can be made thereto without departing from the broader spirit and scope of the implementation of the present disclosure, as set forth in the following claims. Thus, the present specification and drawings should be considered in an illustrative rather than a restrictive sense. In addition, directional terms such as "top" and "bottom" do not limit the scope of the present disclosure to any fixed orientation, but encompass various permutations and combinations of orientations. [Explanation of symbols]

[0033] 100 Embodiments 110 Waveguide-based sensing chip 115 Input / Output Waveguide 120 Input terminal 122 Output terminal 124 Incident guided light, beam 126 Outgoing waveguide light 127 Beam 128 dotted rectangle 128a Dotted area 128b Dotted area, ring-to-ring coupling region 128c Dotted area 130 Waveguide-based resonant ring 130a loss ring 130b Gain ring, loss ring 132 Waveguide 132a Guided light beam 132b Guided optical beams, gain rings, guided beams 200 Embodiments 210 Coupling Ring Integrated Photonics Optical Gyroscope Sensing Chip 215 Waveguide 220 Input terminal 222 Output terminal 224 Pump laser light, beam 226 Emitted Light 227 Beam 300 Embodiments 310a First layer 310b Second layer 328a Dotted outline 328b Dotted outline 330a Dotted outline 400 Embodiments 410 Detection Chip 460 Pump Laser 485 Erbium dopant ion 524 Laser Light 562 Mirror 570 SiN core, waveguide core 570a SiN waveguide cross section, waveguide 570b SiN waveguide cross section, waveguide 570c ​​SiN waveguide cross section, waveguide 570d SiN waveguide cross section, waveguide 580 injection area, injection layer 585 Erbium Ion 600 Embodiments 610a Lower layer 610b Upper layer 700 Embodiments 780 Heater

Claims

1. 1. An integrated photonics 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 output light that is coupled to a photodetector to provide an optical signal for rotation sensing; a first microresonator ring proximate to a portion of the first straight waveguide, where light evanescently couples from the portion of the first straight waveguide into the first microresonator ring and experiences propagation losses as it circulates as a guided beam within the first microresonator ring; a second microresonator ring proximate a portion of the first microresonator ring, the guided beam evanescently coupling from the portion of the first microresonator ring to a portion of the second microresonator ring and experiencing optical gain to counter propagation losses in the first microresonator ring and the second microresonator ring; a pump laser chip physically mounted on a layer including the second microresonator ring, the pump laser chip providing a first pump light that imparts at least a portion of the optical gain to the guided beam; Equipped with an integrated photonics optical gyroscope, wherein an optical gain is imparted to the guided beam to combat the propagation losses, and then the guided beam evanescently couples from the first microresonator ring back to the portion of the first straight waveguide to provide the optical signal for rotation sensing.

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

3. 2. The integrated photonics optical gyroscope of claim 1 , wherein the guided wave beam evanescently couples from the second microresonator ring to the first microresonator ring and back from the first microresonator ring to the portion of the first straight waveguide to provide the optical signal for rotation sensing.

4. 4. The integrated photonics optical gyroscope of claim 3, further comprising a second straight waveguide that receives second pump light from one or more pump light sources, a portion of the second straight waveguide proximate the second microresonator ring, and the pump light providing the optical gain against the propagation losses.

5. The integrated photonics optical gyroscope of claim 1 , wherein the first microresonator ring and the second microresonator ring are identical in shape and size.

6. 10. The integrated photonics optical gyroscope of claim 1, wherein a shape, a size, or both the shape and the size of the first microresonator ring is different from a shape, a size, or both the shape and the size of the second microresonator ring.

7. 2. The integrated photonics optical gyroscope of claim 1 , wherein the first microresonator ring and the second microresonator ring are fabricated on different physical layers vertically stacked on top of each other, and light evanescently couples between the two vertically separated physical layers.

8. The integrated photonics optical gyroscope of claim 7 , wherein the first microresonator ring and the second microresonator ring are laterally offset with respect to one another.

9. 5. The optical gyroscope of claim 4, wherein at least a portion of the second microresonator ring is doped with an erbium dopant that can be excited by a particular wavelength of the first pump light to provide the optical gain.

10. 10. The optical gyroscope of claim 9, wherein the second pump light is coupled into the second microresonator ring from a second straight waveguide into which the second pump light is launched from one or both ends.

11. The optical gyroscope of claim 10 , wherein the pump laser chip is disposed over the portion of the second microresonator ring that is implanted with the erbium dopant.

12. The optical gyroscope of claim 11 , wherein a mirror is fabricated on top of the pump laser chip to improve vertical injection of the first pump light into the erbium dopant.

13. 13. The optical gyroscope of claim 12, wherein the second microresonator ring is fabricated on an upper vertical layer adjacent to the pump laser chip, and the first microresonator ring is fabricated on a lower vertical layer below the upper vertical layer.

14. The optical gyroscope of claim 13 , wherein a heater is fabricated on the top vertical layer to adjust an amount of evanescent coupling between the second microresonator ring and the first microresonator ring.

15. 2. The optical gyroscope of claim 1 , wherein the first microresonator ring and the second microresonator ring are fabricated on a common physical layer, and a heater is fabricated on the common physical layer to adjust an amount of evanescent coupling between the second microresonator ring and the first microresonator ring.

16. 5. The optical gyroscope of claim 4, wherein one of the first and second pump lights of a suitable wavelength is coupled into the second microresonator ring to induce stimulated Raman scattering (SRS) to provide the optical gain.

17. 5. The optical gyroscope of claim 4, wherein one of the first and second pump lights of a suitable wavelength is coupled into the second microresonator ring to induce stimulated Brillouin scattering (SBS) to provide the optical gain.

18. The optical gyroscope of claim 1 , wherein the 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 above.

19. 2. The optical gyroscope of claim 1, wherein at least a portion of the first microresonator ring is doped with an erbium dopant that can be excited by a particular wavelength of the first pump light to provide the optical gain.

20. A coupling-ring integrated photonics 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 output light that is coupled to a photodetector to provide an optical signal for rotation sensing; a first microresonator ring proximate to a portion of the first straight waveguide, where light evanescently couples from the portion of the first straight waveguide into the first microresonator ring and experiences propagation losses as it circulates as a guided beam within the first microresonator ring; a second microresonator ring proximate a portion of the first microresonator ring, the guided beam evanescently coupling from the portion of the first microresonator ring to a portion of the second microresonator ring and experiencing optical gain to counter propagation losses in the first microresonator ring and the second microresonator ring; a pump laser chip physically mounted on a layer including the second microresonator ring, the pump chip providing a first pump light that imparts at least a portion of the optical gain to the guided beam; A coupled-ring integrated photonics optical gyroscope comprising:

21. 21. The coupled-ring-integrated photonics optical gyroscope of claim 20, wherein the guided wave beam evanescently couples from the second microresonator ring to the first microresonator ring and back from the first microresonator ring to the portion of the first straight waveguide to provide the optical signal for rotation sensing.

22. 21. The coupled-ring-integrated photonics optical gyroscope of claim 20, wherein the first microresonator ring and the second microresonator ring are fabricated on different physical layers vertically stacked on top of each other, and light evanescently couples between the two vertically separated physical layers.

23. 22. The coupled-ring-integrated photonics optical gyroscope of claim 21, further comprising a second straight waveguide that receives second pump light from one or more pump light sources, a portion of the second straight waveguide being proximate to the second microresonator ring, the second pump light providing the optical gain against the propagation losses.

24. 24. The coupled-ring-integrated photonics optical gyroscope of claim 23, wherein at least a portion of the second microresonator ring is implanted with an erbium dopant that can be excited at a particular wavelength of the first pump light to provide the optical gain.

25. 25. The coupled-ring integrated photonics optical gyroscope of claim 24, wherein the first pump light is coupled into the second microresonator ring from at least one side to excite the erbium dopant.

26. 25. The coupled-ring integrated photonics optical gyroscope of claim 24, wherein the second pump light is coupled into the second microresonator ring from above to excite the erbium dopant.

27. 25. The coupled-ring integrated photonics optical gyroscope of claim 24, wherein the second pump light is at a wavelength that depends on a wavelength of excitation for the erbium dopant.

28. 24. The coupled-ring-integrated photonics optical gyroscope of claim 23, wherein one of the first and second pump lights of a suitable wavelength is coupled into the second microresonator ring to induce stimulated Raman scattering (SRS) to provide the optical gain.

29. 24. The coupled-ring-integrated photonics optical gyroscope of claim 23, wherein one of the first and second pump lights of a suitable wavelength is coupled into the second microresonator ring to induce stimulated Brillouin scattering (SBS) to provide the optical gain.

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