An optical fiber gyroscope integrated photon chip

Abstract

This disclosure relates to the fields of integrated optics and fiber optic gyroscope technology, and to, but is not limited to, a fiber optic gyroscope integrated photonic chip. The integrated photonic chip comprises: a first dielectric layer and a second dielectric layer stacked sequentially along a first direction; a silicon nitride waveguide component and a silicon nitride coupler connected thereto are formed within the first dielectric layer; a thin-film lithium tantalate waveguide is formed within the second dielectric layer and connected thereto by a thin-film lithium tantalate coupler; the silicon nitride coupler and the thin-film lithium tantalate coupler are projected and aligned along the first direction, and the silicon nitride coupler and the thin-film lithium tantalate coupler are coupled together. The silicon nitride waveguide component carries the main functions of transmission, beam splitting and combining, and polarization management within the chip. Silicon nitride has low propagation loss and a scalable manufacturing process, which helps reduce system insertion loss. Thin-film lithium tantalate can reduce the drift risk under high optical power, thereby improving the feasibility of long-term stability and consistency of the fiber optic gyroscope integrated photonic chip.

Description

Technical Field

[0001] This disclosure relates to the fields of integrated optics and fiber optic gyroscope technology, and to, but is not limited to, a fiber optic gyroscope integrated photonic chip. Background Technology

[0002] Fiber Optic Gyroscopes (FOGs), as the core category of optical gyroscopes, achieve high-precision angular velocity measurement based on the Sagnac effect. They feature anti-electromagnetic interference, high reliability, and long lifespan, and are widely used in inertial navigation, attitude measurement, and high-reliability industrial measurement scenarios. They play an important supporting role in improving the navigation, positioning, and attitude perception performance of high-end equipment.

[0003] However, existing fiber optic gyroscope systems mostly use discrete optical and fiber optic devices to build the core optical path. This significantly limits system size, assembly complexity, and batch consistency. Currently, technologies have been proposed to replace some discrete devices with integrated optical chips for fiber optic gyroscopes, but these are prone to long-term instability issues caused by material effects and bias drift. Furthermore, silicon nitride, as a passive low-loss platform, lacks efficient electro-optic modulation capabilities, and its heterogeneous integration with thin-film lithium niobate makes it difficult to balance low-loss interconnection with engineering reliability. Summary of the Invention

[0004] This disclosure provides an integrated photonic chip for a fiber optic gyroscope, comprising: a first dielectric layer and a second dielectric layer stacked sequentially along a first direction; the first direction is perpendicular to the plane in which the first dielectric layer is located; A silicon nitride waveguide assembly and a silicon nitride coupler are formed within the first dielectric layer, and the silicon nitride coupler is connected to the silicon nitride waveguide assembly; A thin-film lithium tantalate waveguide and a thin-film lithium tantalate coupler are formed within the second dielectric layer; the thin-film lithium tantalate coupler is connected to the thin-film lithium tantalate waveguide. The silicon nitride coupler and the thin-film lithium tantalate coupler are aligned by projection along a first direction, and the silicon nitride coupler is coupled to the thin-film lithium tantalate coupler.

[0005] In this embodiment of the disclosure, the silicon nitride waveguide assembly includes an input silicon nitride waveguide assembly and a silicon nitride branch waveguide; the input silicon nitride waveguide assembly is connected to the silicon nitride branch waveguide, and the silicon nitride branch waveguide is connected to the silicon nitride coupler.

[0006] In this embodiment of the disclosure, the input silicon nitride waveguide assembly includes a first multimode interference coupler, a polarization multiplexer, and a second multimode interference coupler that are optically connected sequentially along the optical path transmission direction through the main silicon nitride waveguide; the second multimode interference coupler is connected to the silicon nitride branch waveguide.

[0007] In this embodiment of the disclosure, the silicon nitride coupler includes a first silicon nitride coupler and a second silicon nitride coupler; The silicon nitride branch waveguide includes a first branch silicon nitride waveguide and a second branch silicon nitride waveguide; one end of the first branch silicon nitride waveguide is connected to the second multimode interference coupler, and the other end of the first branch silicon nitride waveguide is connected to the first silicon nitride coupler; one end of the second branch silicon nitride waveguide is connected to the second multimode interference coupler, and the other end of the second branch silicon nitride waveguide is connected to the second silicon nitride coupler.

[0008] In this embodiment of the disclosure, the thin-film lithium tantalate coupler includes a first thin-film lithium tantalate coupler and a second thin-film lithium tantalate coupler; the thin-film lithium tantalate waveguide includes a first thin-film lithium tantalate waveguide and a second thin-film lithium tantalate waveguide arranged in parallel. One end of the first thin-film lithium tantalate waveguide is connected to the first thin-film lithium tantalate coupler, and one end of the second thin-film lithium tantalate waveguide is connected to the second thin-film lithium tantalate coupler. The first thin-film lithium tantalate coupler and the first silicon nitride coupler are arranged opposite to each other along a first direction and are coupled together, thereby coupling the first thin-film lithium tantalate waveguide to the first branch silicon nitride waveguide. The second thin-film lithium tantalate coupler and the second silicon nitride coupler are arranged opposite to each other along the first direction and are coupled together, thereby coupling the second thin-film lithium tantalate waveguide to the second branch silicon nitride waveguide.

[0009] In this embodiment of the present disclosure, the fiber optic gyroscope integrated photonic chip further includes an end-face coupler; the number of the end-face couplers is multiple, and the multiple end-face couplers are respectively connected to the thin-film lithium tantalate waveguide and the silicon nitride waveguide assembly, and are used to couple with external optical fibers or external optical paths.

[0010] In this embodiment of the disclosure, the end-face coupler includes a first end-face coupler, a second end-face coupler, a third end-face coupler, and a fourth end-face coupler; The first end-face coupler and the second end-face coupler are respectively coupled to the first multimode interference coupler; The thin-film lithium tantalate coupler further includes a third thin-film lithium tantalate coupler and a fourth thin-film lithium tantalate coupler; the third thin-film lithium tantalate coupler is connected to the other end of the first thin-film lithium tantalate waveguide, and the fourth thin-film lithium tantalate coupler is connected to the other end of the second thin-film lithium tantalate waveguide; The third end face coupler is coupled to the third thin-film lithium tantalate coupler, and the fourth end face coupler is coupled to the fourth thin-film lithium tantalate coupler.

[0011] In this embodiment of the present disclosure, a first ground electrode is disposed along a first direction of the first thin-film lithium tantalate waveguide; a signal electrode is disposed along a first direction between the first thin-film lithium tantalate waveguide and the second thin-film lithium tantalate waveguide; and a second ground electrode is disposed along a first direction of the second thin-film lithium tantalate waveguide.

[0012] In this embodiment, the cross-sectional shape of the silicon nitride coupler is one or a combination of two of the following: tapered or rectangular. The cross-sectional shape of the thin-film lithium tantalate coupler is consistent with that of the silicon nitride coupler.

[0013] In this embodiment of the disclosure, the first dielectric layer is formed on the upper surface of the silicon substrate along the first direction; the material of the first dielectric layer and the second dielectric layer is silicon oxide.

[0014] An embodiment of the fiber optic gyroscope integrated photonic chip disclosed herein comprises a silicon nitride waveguide component and a thin-film lithium tantalate waveguide formed in a first dielectric layer and a second dielectric layer stacked sequentially along a first direction, respectively. Interlayer coupling between the silicon nitride waveguide component and the thin-film lithium tantalate waveguide is achieved through a silicon nitride coupler connected to the silicon nitride waveguide and a thin-film lithium tantalate coupler connected to the thin-film lithium tantalate waveguide. The silicon nitride waveguide component carries the main transmission, beam splitting and combining, and polarization management functions within the fiber optic gyroscope integrated photonic chip. The silicon nitride platform has a low propagation loss and a scalable manufacturing process, which is beneficial for reducing system insertion loss and improving batch consistency. The thin-film lithium tantalate can reduce the drift risk under high optical power operation, thereby improving the feasibility of long-term stable operation and consistency of the fiber optic gyroscope integrated photonic chip. Attached Figure Description

[0015] Figure 1 A schematic diagram of the architecture of a fiber optic gyroscope integrated photonic chip provided in this embodiment of the disclosure; Figure 2 A schematic diagram of a first dielectric layer and a second dielectric layer provided in an embodiment of this disclosure. Figure 1 ; Figure 3 A schematic diagram of a first dielectric layer and a second dielectric layer provided in an embodiment of this disclosure. Figure 2 ; Figure 4 A cross-sectional schematic diagram of a fiber optic gyroscope integrated photonic chip provided in an embodiment of this disclosure; Figure 5 This is a schematic diagram of the coupling between a thin-film lithium tantalate waveguide and a silicon nitride branch waveguide provided in an embodiment of this disclosure; Figure 6 A top view schematic diagram of an integrated photonic chip for a fiber optic gyroscope provided in an embodiment of this disclosure; Figure 7This is a schematic diagram of the internal electrode architecture of an integrated photonic chip for a fiber optic gyroscope, provided as an embodiment of the present disclosure.

[0016] Explanation of reference numerals in the attached figures: Detailed Implementation

[0017] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the specific embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0018] In the following description, numerous specific details are set forth in order to provide a more thorough understanding of this disclosure. However, it will be apparent to those skilled in the art that this disclosure may be practiced without one or more of these details. In other instances, to avoid confusion with this disclosure, certain technical features well-known in the art have not been described; that is, not all features of actual embodiments are described herein, nor are well-known functions and structures described in detail.

[0019] In the accompanying drawings, for clarity, the dimensions of layers, areas, and elements, as well as their relative dimensions, may be exaggerated. The same reference numerals denote the same elements throughout.

[0020] It should be understood that when an element or layer is referred to as "on," "adjacent to," "connected to," or "coupled to" other elements or layers, it may be directly on, adjacent to, connected to, or coupled to other elements or layers, or there may be intervening elements or layers. Conversely, when an element is referred to as "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" other elements or layers, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc., may be used to describe various elements, components, areas, layers, and / or portions, these elements, components, areas, layers, and / or portions should not be limited by these terms. These terms are only used to distinguish one element, component, area, layer, or portion from another element, component, area, layer, or portion. Therefore, without departing from the teachings of this disclosure, the first element, component, area, layer, or portion discussed below may be referred to as a second element, component, area, layer, or portion. And the discussion of a second element, component, area, layer, or portion does not imply that the first element, component, area, layer, or portion necessarily exists in this disclosure.

[0021] Spatial relation terms such as “below,” “under,” “below,” “below,” “above,” “above,” etc., are used herein for convenience of description to describe the relationship between one element or feature shown in the figure and other elements or features. It should be understood that, in addition to the orientation shown in the figure, spatial relation terms are intended to also include different orientations of the device in use and operation. For example, if the device in the figure is flipped, then the element or feature described as “below” or “below” other elements or features will be oriented “above” other elements or features. Therefore, the exemplary terms “below” and “under” can include both upper and lower orientations. The device may be otherwise oriented (rotated 90 degrees or otherwise) and the spatial descriptive terms used herein will be interpreted accordingly.

[0022] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. When used herein, the singular forms “a,” “an,” and “ / the” are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprise” and / or “comprising,” when used in this specification, identify the presence of features, integers, steps, operations, elements, and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts, and / or groups. When used herein, the term “and / or” includes any and all combinations of the associated listed items.

[0023] To provide a more detailed understanding of the features and technical content of the embodiments of this disclosure, the implementation of the embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. The accompanying drawings are for reference only and are not intended to limit the embodiments of this disclosure. In the following disclosed embodiments, the first direction can be the Z-axis direction in the accompanying drawings, and the second direction can be the X-direction in the accompanying drawings.

[0024] Most fiber optic gyroscope systems employ discrete optical and fiber optic components to achieve core functions such as beam splitting and combining, polarization state management, phase modulation, and photoelectric detection. This significantly limits the overall system size, assembly complexity, and batch consistency. To meet the application requirements of miniaturization, integration, and high batch consistency in fiber optic gyroscopes, existing technologies have proposed replacing some discrete components with integrated optical chips (IOCs). Among these, lithium niobate (LN) electro-optic modulators, due to their significant linear electro-optic effect and high modulation bandwidth, are widely used in external modulation scenarios and have achieved large-scale application in fiber optic gyroscopes and related sensing systems.

[0025] With the continuous development of thin-film lithium niobate integrated photonics technology, high-speed, compact electro-optic devices based on thin-film lithium niobate have attracted widespread attention in this field. However, in addition to the technical bottlenecks of process uniformity and long-term engineering reliability, the thin-film lithium niobate material platform also has complex inherent material effects such as pyroelectric effect and photorefractive effect. Under actual operating conditions of light and ambient temperature changes, these effects may cause internal operating point drift, increased additional noise, and long-term memory effects, which will have a significant adverse impact on high-precision applications that require long-term stable operating point maintenance. At the same time, lithium niobate electro-optic devices exhibit the well-known "DC drift / operating point drift" phenomenon in terms of DC bias or operating point control. The time scale of this drift can reach from minutes to hours or even longer. Existing solutions require additional bias control modules or improvements to device structure and fabrication processes to maintain long-term stable operation of the device. The aforementioned drift and stability issues may further manifest in high-precision fiber optic gyroscope systems as deterioration of zero-bias stability, increase in low-frequency noise, and decrease in batch consistency, among other engineering application risks.

[0026] On the other hand, silicon nitride (Si3N4) photonic integration platforms have become a key research direction in this field due to their low optical propagation loss, ability to fabricate high-Q-factor (High Quality Factor) optical devices, and inherent material properties suitable for long optical paths and low-loss optical transmission. They can provide a low-loss carrier for passive functions such as beam splitting and combining and optical path transmission in fiber optic gyroscope integrated optical chips. However, silicon nitride itself lacks a significant linear electro-optic effect, making it difficult to independently achieve high-efficiency phase modulation functions. Therefore, this disclosure proposes to heterogeneously integrate a low-loss passive material platform with a material with a strong electro-optic effect, and achieve the synergistic integration of passive optical functions and active modulation functions through wafer-level bonding or material transfer processes.

[0027] In summary, the integrated development of photonic chips for fiber optic gyroscopes still faces the following core technical challenges: First, discrete fiber optic gyroscope systems suffer from large size and high assembly complexity, making it difficult to meet the demands of miniaturized, highly consistent, and mass-produced applications. Second, electro-optic integration schemes based on lithium niobate and thin-film lithium niobate are limited by the inherent pyroelectric effect, photorefractive effect, and DC drift characteristics of the materials, resulting in insufficient long-term operational stability and failing to meet the long-term stable operation requirements of high-precision fiber optic gyroscopes. Third, low-loss passive platforms based on silicon nitride are limited by the electro-optic properties of the material itself, making it impossible to independently achieve efficient electro-optic modulation. Furthermore, multi-material heterogeneous integration schemes face challenges in simultaneously achieving low-loss interconnection, process compatibility, and engineering reliability. Therefore, there is an urgent need in this field for a fiber optic gyroscope integrated photonic chip solution that can simultaneously achieve low-loss passive optical transmission and efficient on-chip phase modulation, while also possessing superior long-term operational stability and engineering feasibility in high-precision application scenarios.

[0028] Based on this, embodiments of this disclosure provide a fiber optic gyroscope integrated photonic chip, such as... Figure 1 As shown, it includes: a first dielectric layer 1 and a second dielectric layer 2 stacked sequentially along a first direction; the first direction is perpendicular to the plane where the first dielectric layer 1 is located; Within the first dielectric layer 1, a silicon nitride waveguide component 10 and a silicon nitride coupler 31 are formed using semiconductor integration processes such as photolithography and etching. The silicon nitride coupler 31 is connected to the silicon nitride waveguide component 10. The arrangement position and mode field structure of the silicon nitride coupler 31 are adapted to the silicon nitride waveguide component 10. Specifically, it is directly optically connected to the transmission end of the silicon nitride waveguide component 10, and the silicon nitride coupler 31 provides a stable mode field matching basis for interlayer optical signal coupling.

[0029] Within the second dielectric layer 2, a thin-film lithium tantalate waveguide 20 and a thin-film lithium tantalate coupler 32 are formed using a corresponding semiconductor integration process. Simultaneously, the placement and mode field structure of the thin-film lithium tantalate coupler 32 are adapted to the thin-film lithium tantalate waveguide 20.

[0030] The size, shape, mode field distribution, and placement of the thin-film lithium tantalate coupler 32 are all compatible with those of the silicon nitride coupler 31. The thin-film lithium tantalate coupler 32 and the silicon nitride coupler 31 are arranged opposite each other along the first direction, so that the projections of the thin-film lithium tantalate coupler 32 and the silicon nitride coupler 31 along the first direction are precisely aligned. This ensures that when optical signals are transmitted across layers within the chip, the silicon nitride coupler 31 and the thin-film lithium tantalate coupler 32 achieve efficient coupling, and the thin-film lithium tantalate coupler 32 and the thin-film lithium tantalate waveguide 20 achieve low-loss optical connectivity.

[0031] It is understood that the number, branch structure, and arrangement of the silicon nitride waveguide component 10 and silicon nitride coupler 31 can be flexibly set according to the actual chip integration requirements, substrate size, and fiber optic gyroscope optical path topology. There can be one group or multiple groups. Multiple groups of waveguides and couplers can be arranged in a symmetrical and uniform distribution, corresponding to the closed-loop structure of the gyroscope optical path. Similarly, the number of thin-film lithium tantalate waveguides 20 and thin-film lithium tantalate couplers 32 can also be flexibly adjusted based on the overall optical path modulation efficiency and signal transmission accuracy requirements. There can be one group or multiple groups. Multiple groups of thin-film lithium tantalate waveguides 20 and couplers can be arranged at preset optical path spacing intervals, forming a one-to-one correspondence with the waveguides and couplers on the silicon nitride side. Other waveguide coupling structures that can achieve low-loss coupling of cross-layer optical signals can also be considered as the coupler structures of this disclosure. Their optical path connectivity and mode field matching functions are essentially similar to those of the silicon nitride coupler 31 and thin-film lithium tantalate coupler 32 of this disclosure.

[0032] Among them, silicon nitride waveguide components carry the main transmission, beam splitting and combining, polarization management and other functions in the fiber optic gyroscope integrated photonic chip. The silicon nitride platform has the process basis of low propagation loss and scalable manufacturing, which is conducive to reducing system insertion loss and improving batch consistency. Thin film lithium tantalate can reduce the drift risk under high optical power operation, thereby improving the feasibility of long-term stable operation and consistency of the fiber optic gyroscope integrated photonic chip.

[0033] In the embodiments disclosed herein, such as Figure 2 As shown, the silicon nitride waveguide assembly 10 includes an input silicon nitride waveguide assembly 11 and a silicon nitride branch waveguide 12. The output end of the input silicon nitride waveguide assembly 11 is directly optically connected to the input end of the silicon nitride branch waveguide 12. The specific configuration of the input silicon nitride waveguide assembly 11 and the connection position of the branch waveguide can be flexibly adjusted according to the input and output requirements and beam splitting ratio of the actual optical path of the fiber optic gyroscope, providing a stable optical transmission foundation for signal beam splitting and beam combining in the gyroscope optical path.

[0034] The output end of the silicon nitride branch waveguide 12 is optically connected to the input end of the silicon nitride coupler 31. The number of branches, the position of the output end, and the waveguide mode field parameters of the silicon nitride branch waveguide 12 are all adapted to the number, position, and mode field structure of the silicon nitride coupler 31, so as to realize the connection between the silicon nitride branch waveguide 12 and the silicon nitride coupler 31.

[0035] Understandably, the number of ports of the input silicon nitride waveguide component 11, the specific device configuration, and the number of branches, beam splitting ratio, and arrangement of the silicon nitride branch waveguide 12 can be flexibly set according to the actual closed-loop optical path design requirements, chip integration, and substrate size of the fiber optic gyroscope. The input silicon nitride waveguide component 11 can be a single-path input structure or a multi-path differential input structure, and the silicon nitride branch waveguide 12 can be a 1×2 symmetrical beam splitting structure or a 1×N multi-path beam splitting structure. Similarly, the connection method between the silicon nitride branch waveguide 12 and the silicon nitride coupler 31 can also be flexibly adjusted based on the overall optical path transmission loss and polarization consistency requirements.

[0036] In this disclosure, see also the embodiments described above. Figure 2 The input silicon nitride waveguide assembly 11 includes a first multimode interference coupler 112, a polarization multiplexer 113, and a second multimode interference coupler 114 that are optically connected sequentially through the main silicon nitride waveguide 111 along the optical path transmission direction. The port of the first multimode interference coupler 112 is adapted to the output end of the external optical fiber and the input end of the polarization multiplexer 113, and is specifically optically connected to the input end of the polarization multiplexer 113.

[0037] The core structural parameters of the first multimode interference coupler 112, such as the length, width, and port spacing, can be flexibly adjusted according to the polarization control requirements of the actual optical path of the fiber optic gyroscope and the mode matching requirements of the input optical signal. This provides a stable mode matching and low-loss access foundation for the optical signal input from the external optical fiber. The main silicon nitride waveguide 111 can be set with bending radius and spacing according to chip layout requirements, and forms a functional link with the first multimode interference coupler 112, polarization multiplexer 113, and second multimode interference coupler 114. The specific dimensions of each device can be conventionally designed and optimized according to the target wavelength and process capabilities.

[0038] The number of output ports of the second multimode interference coupler 114 is the same as the number of input ports of the silicon nitride branch waveguide 12, so that the second multimode interference coupler 114 and the silicon nitride branch waveguide 12 are connected. The structural parameters of the polarization multiplexer 113 are adapted to the polarization state control requirements of the fiber optic gyroscope optical path, ensuring that the optical signal input from the external fiber enters the first multimode interference coupler 112 through the main silicon nitride waveguide 111 to complete mode matching and beam splitting, and then completes the unified control and beam combining of polarization state through the polarization multiplexer 113 before being transmitted to the second multimode interference coupler 114. Finally, the power is distributed through the second multimode interference coupler 114 and output to the silicon nitride branch waveguide 12.

[0039] It should be noted that, depending on the actual optical path requirements, suitable passive optical devices such as transition tapered waveguides, on-chip optical attenuators, micro-ring resonators, and polarization controllers can also be inserted, which does not constitute the sole limitation of this invention.

[0040] In this disclosure, see also the embodiments described above. Figure 2 The silicon nitride coupler 31 formed within the first dielectric layer 1 includes a first silicon nitride coupler 311 and a second silicon nitride coupler 312; correspondingly, the silicon nitride branch waveguide 12 includes a first branch silicon nitride waveguide 121 and a second branch silicon nitride waveguide 122. One end of the first branch silicon nitride waveguide 121 is optically connected to the corresponding output end of the second multimode interference coupler 114, while the other end is optically connected to the input end of the first silicon nitride coupler 311; one end of the second branch silicon nitride waveguide 122 is optically connected to the other corresponding output end of the second multimode interference coupler 114, and the other end of the second branch silicon nitride waveguide 122 is optically connected to the second silicon nitride coupler 312. The pairing arrangement of the silicon nitride branch waveguide 12 and the silicon nitride coupler 31 allows for flexible adjustment of the bending path, transmission length, and spacing of the silicon nitride branch waveguide 12 and the silicon nitride coupler 31 according to the actual closed-loop optical path transmission requirements of the fiber optic gyroscope and the cross-layer coupling point layout. This ensures that the beam splitting uniformity of the second multimode interference coupler 114 and the low-loss transmission performance of the overall optical path are not compromised, while also providing a stable optical transmission foundation for the synchronous cross-layer coupling of multiple optical signals to the second dielectric layer 2.

[0041] It is understood that the number of paired silicon nitride branch waveguides 12 and silicon nitride couplers 31 in this embodiment does not constitute the only limitation of this disclosure. The specific number can be flexibly set according to the actual optical path topology design of the fiber optic gyroscope, chip integration, detection accuracy requirements, and the number of cross-layer coupling points. It can be 2 groups as shown in this embodiment, or 1 group, 3 groups, or even N groups, where N is a positive integer. Multiple groups of silicon nitride branch waveguides 12 and silicon nitride couplers 31 can be paired and connected in a one-to-one manner, and are fully compatible with the multi-channel output of the second multimode interference coupler 114. The arrangement of the branch waveguides can be symmetrical parallel arrangement, or ring arrangement, differential pairing arrangement, grouping arrangement along the chip edge, and other methods.

[0042] It should be noted that, between the single-path silicon nitride branch waveguide 12 and the single silicon nitride coupler 31, auxiliary optical devices such as transition tapered waveguides, polarization fine-tuning structures, and optical power monitoring structures can also be inserted according to actual optical path requirements, without being limited to the direct connection structure shown in this embodiment; as long as the stable transmission function of the optical signal from the second multimode interference coupler 114 to the corresponding coupler can be achieved, it falls within the protection scope of this disclosure. This disclosure does not impose a unique limitation on the number, arrangement, and connection form of the silicon nitride branch waveguides 12 and the silicon nitride couplers 31.

[0043] In the embodiments disclosed herein, such as Figure 3As shown, the thin-film lithium tantalate coupler 32 formed in the second dielectric layer 2 includes a first thin-film lithium tantalate coupler 321 and a second thin-film lithium tantalate coupler 322; correspondingly, the thin-film lithium tantalate waveguide 20 includes a first thin-film lithium tantalate waveguide 201 and a second thin-film lithium tantalate waveguide 202.

[0044] The first thin-film lithium tantalate coupler 321 is optically connected to the end of the first thin-film lithium tantalate waveguide 201 closest to the first silicon nitride coupler 311. The first thin-film lithium tantalate waveguide 201 is located within the second dielectric layer 2, and the first silicon nitride coupler 311 is located within the first dielectric layer 1. (See also...) Figure 4 As shown, the first thin-film lithium tantalate coupler 321 and the first silicon nitride coupler 311 are arranged opposite each other along the first direction, so that the first branch silicon nitride waveguide 121 and the first thin-film lithium tantalate waveguide 201 are interlayer coupled; similarly, since the second thin-film lithium tantalate coupler 322 is optically connected to the end of the second thin-film lithium tantalate waveguide 202 near the second silicon nitride coupler 312, and based on the reason that the second thin-film lithium tantalate waveguide 202 is located in the second dielectric layer 2, the second thin-film lithium tantalate waveguide 202 and the second branch silicon nitride waveguide 122 are interlayer coupled.

[0045] It is understandable that the specific number of thin-film lithium tantalate waveguides 20 is consistent with the number of silicon nitride branch waveguides 12. The specific pairing number of the two can be flexibly set and dynamically adjusted according to the actual optical path topology design of the fiber optic gyroscope, phase modulation accuracy requirements, chip integration index, and multi-axis gyroscope integration requirements.

[0046] It should be noted that, under the premise of meeting the transmission requirements of the core optical path, the single-path thin-film lithium tantalate waveguide 20 can be configured into various structural forms such as segmented waveguides and bent waveguides according to the actual electro-optic modulation requirements. Its overall structure still belongs to the single-path waveguide structure that matches the number of corresponding silicon nitride branch waveguides 12, without changing the numerical correspondence between the two. At the same time, the structural parameters of the thin-film lithium tantalate waveguide 20, such as cross-sectional dimensions, waveguide length, bending radius, and refractive index distribution, can be flexibly adapted and adjusted to the parameters of the corresponding silicon nitride branch waveguide 12. It does not need to be completely consistent with the physical dimensions of the silicon nitride branch waveguide 12. This disclosure does not make a unique limitation in this regard.

[0047] In this disclosure embodiment, see Figure 1The optical end face of the fiber optic gyroscope integrated photonic chip provided in this embodiment is formed by semiconductor integration and back-end processes such as photolithography, etching, thin film deposition, and end face polishing. The number of multi-face couplers is multiple, and the multiple end face couplers 4 are respectively connected to the output end of the thin film lithium tantalate waveguide 20 and the input end of the first multimode interference coupler 112 in the silicon nitride waveguide assembly 10. The optical path input end of the end face coupler 4 is directly optically connected to the front end of the input silicon nitride waveguide assembly 11 in the first dielectric layer 1 of the chip, so that the external optical fiber or external optical path enters the silicon nitride waveguide assembly 10. The end face coupler 4 is also optically connected to the output end of the thin film lithium tantalate waveguide 20 in the second dielectric layer 2, so that the optical signal in the fiber optic gyroscope integrated photonic chip is output to the external optical fiber or external optical path.

[0048] It is understood that the structure, number, arrangement, and waveguide material system of the end-face coupler 4 in this embodiment are not the sole limitation on the scope of protection of this disclosure, and can be flexibly set and adjusted according to the actual chip integration, multi-axis optical path design, and packaging form of the fiber optic gyroscope.

[0049] In this disclosure embodiment, see Figure 6 The end-face coupler 4 includes a first end-face coupler 41, a second end-face coupler 42, a third end-face coupler 43, and a fourth end-face coupler 44; wherein the output ends of the first end-face coupler 41 and the second end-face coupler 42 are optically coupled to the input end of the first multimode interference coupler 112, respectively.

[0050] It is understandable that using two end-face couplers 4 to share the same first multimode interference coupler 112 is to adapt to the optical path reciprocity requirements of high-precision fiber optic gyroscopes. It can rely on the inherent symmetrical beam splitting and completely consistent optical path characteristics of multimode interference couplers to ensure that the transmission paths of the forward input light and the reverse signal light are symmetrical and the beam splitting characteristics are matched from the structure. Otherwise, structural size deviations caused by semiconductor processing may lead to inconsistent beam splitting ratios and optical path differences, thereby degrading the performance indicators of the gyroscope such as zero-bias stability and random walk coefficient.

[0051] Furthermore, the thin-film lithium tantalate coupler 32 is located at both ends of the thin-film lithium tantalate waveguide 20, thereby realizing the input and output of optical signals within the thin-film lithium tantalate waveguide 20. Therefore, the thin-film lithium tantalate waveguide 20 also includes a third thin-film lithium tantalate coupler 323 and a fourth thin-film lithium tantalate coupler 324. The input end of the third end-face coupler 43 is connected to the output end of the third thin-film lithium tantalate coupler 323, and the input end of the fourth end-face coupler 44 is optically coupled to the output end of the fourth thin-film lithium tantalate coupler 324, so that the two interference optical signals after electro-optic modulation are output.

[0052] It should be noted that the first end-face coupler 41, the second end-face coupler 42, the third end-face coupler 43, and the fourth end-face coupler 44 can adopt an end-face mode conversion structure to achieve coupling with external optical fibers; they can optionally adopt a combination of a tapered transition section and an extended mode section to adapt to the external optical fiber mode field.

[0053] In this disclosure embodiment, see Figure 7 An electrode 5 is provided along the first direction of the first thin-film lithium tantalate waveguide 201, specifically including a first ground electrode 51; a signal electrode 52 is provided along the first direction between the first thin-film lithium tantalate waveguide 201 and the second thin-film lithium tantalate waveguide 202; and a second ground electrode 53 is provided along the first direction of the second thin-film lithium tantalate waveguide 202, which together constitute a phase modulation structure.

[0054] It is understandable that the first thin-film lithium tantalate waveguide 201 and the second thin-film lithium tantalate waveguide 202 serve as two optical paths, respectively. Push-pull modulation is achieved by applying modulation signals with equal amplitude and opposite phase to the two arms, thereby improving the equivalent modulation efficiency and suppressing common-mode disturbances. The first ground electrode 51, the signal electrode 52 and the second ground electrode 53 can be extended in the propagation direction to form the modulation section length, and the electric field distribution and process manufacturability requirements can be met by adjusting the electrode spacing and metal thickness.

[0055] In this embodiment, the cross-sectional shape of the silicon nitride coupler 31 is one or a combination of a cone or rectangle. The cross-sectional shape of the thin-film lithium tantalate coupler 32 and the silicon nitride coupler 31 are consistent, and they are aligned by projection along the first direction to form a shape as shown. Figure 6 The interlayer coupling region A shown enables cross-layer coupling transmission of optical signals between a silicon nitride waveguide and a thin-film lithium tantalate waveguide. The structure, cross-sectional parameters, and coupling region design of this coupler can be flexibly adjusted according to the coupling efficiency, transmission bandwidth, processing tolerance, and polarization consistency requirements of the fiber optic gyroscope optical path.

[0056] In one alternative embodiment of this disclosure, see Figure 5 In (A), the cross-sectional shape of the silicon nitride coupler 31 is conical, meaning that both the silicon nitride coupler 31 and the thin-film lithium tantalate coupler 32 adopt a gradually tapered conical structure, which is an adiabatic mode switching scheme. Correspondingly, the two are provided with an overlapping coupling segment L1 of a preset length along the light propagation direction, and as... Figure 5As shown in (B), the length of the thin-film lithium tantalate coupler is L2, and the length of the silicon nitride coupler is L3. L2 and L3 are aligned and partially overlapped along the first direction for optical coupling. The optical signal mode can also be smoothly transitioned from the silicon nitride dielectric layer to the thin-film lithium tantalate dielectric layer, or vice versa, by gradually changing the waveguide cross-sectional dimensions and adjusting the effective refractive index along the propagation direction. It is understood that the core parameters of this adiabatic mode-conversion coupling structure, such as the tapered start and end widths, the length of the overlapping coupling section, and the effective interlayer spacing of the upper and lower couplers, can be flexibly optimized and adjusted according to the target coupling loss, operating bandwidth, and processing capabilities, without being limited to a fixed parameter range. Furthermore, the tapered gradient can be linear, nonlinear, or segmented, etc., as long as the adiabatic smooth mode conversion can be achieved through effective refractive index gradient, it falls within the protection scope of this disclosure.

[0057] In another optional embodiment of this disclosure, the cross-sectional shape of the silicon nitride coupler 31 is rectangular, meaning that both the silicon nitride coupler 31 and the thin-film lithium tantalate coupler 32 adopt rectangular interlayer coupling, i.e., a directional coupling scheme. Correspondingly, the silicon nitride coupler 31 and the thin-film lithium tantalate coupler 32 maintain a relatively constant effective coupling distance and coupling length within the coupling section, achieving optical energy exchange between the upper and lower waveguides through evanescent wave coupling, thus completing the cross-layer coupling transmission of optical signals. It is understood that the core parameters of this directional coupling structure, such as the coupling length, effective interlayer coupling distance, and waveguide cross-sectional dimensions, can be flexibly set according to the target coupling ratio, operating wavelength, and polarization characteristic requirements. It can be set as a near-fully coupled transmission structure or a coupling structure with a specific beam splitting ratio, without being limited to the fixed parameters of the example in this embodiment. The waveguide structure of the coupling section can be a straight waveguide structure or a curved waveguide structure, as long as interlayer optical signal coupling can be achieved through energy exchange in a fixed coupling section, it falls within the protection scope of this disclosure.

[0058] In another optional embodiment of this disclosure, the cross-sectional shape of the silicon nitride coupler 31 is a gradually tapered and rectangular spliced ​​structure. That is, both the silicon nitride coupler 31 and the thin-film lithium tantalate coupler 32 adopt a gradually tapered and rectangular combined structure for interlayer coupling, which is a multi-segment composite coupling scheme. Correspondingly, within the same interlayer coupling region A, the aforementioned gradually tapered segments and constant coupling segments are combined to form a composite coupling structure that combines adiabatic mode conversion and directional coupling characteristics. This balances chip fabrication process tolerance and target coupling efficiency, while optimizing coupling bandwidth and polarization-dependent loss. It is understood that the number, arrangement order, segment length, and structural parameters of the gradually tapered and constant coupling segments in this composite coupling structure can be flexibly combined and adjusted according to actual optical path requirements and fabrication capabilities. As long as interlayer optical signal coupling can be achieved through the combination of gradually tapered and constant coupling segments, it falls within the protection scope of this disclosure.

[0059] In this embodiment, the number of interlayer coupling regions A corresponding to any of the above coupling methods can be flexibly set according to the actual optical path topology design of the fiber optic gyroscope, multi-channel interconnection requirements, and chip integration density. It can be set to two, three, four, or even more locations. When four coupling regions are used, multi-point synchronous interconnection from the silicon nitride waveguide network to the thin-film lithium tantalate modulation waveguide segment can be achieved, thus facilitating the organization of dual-channel, four-channel, or even multi-channel closed-loop interference optical paths within the chip, perfectly adapting to the integrated photonic chip optical path design requirements of single-axis, dual-axis, and multi-axis fiber optic gyroscopes.

[0060] It should be noted that, in any of the above coupling methods, the cross-sectional shapes of the silicon nitride coupler 31 and the thin-film lithium tantalate coupler 32 can be flexibly selected according to actual coupling requirements. They can be a single conical or rectangular structure throughout, or a combination of conical and rectangular structures, as long as the cross-sectional shapes of the two within the coupling region are matched to achieve efficient interlayer coupling. This disclosure does not impose a unique limitation on this. For example... Figure 5 As shown in (A), setting the width W2 of the thin-film lithium tantalate coupler to be greater than the width W1 of the silicon nitride coupler is a conventional technique in the field to achieve mode field size matching and low-loss thermal insulation cross-layer coupling between two waveguides. It can effectively optimize the inter-layer mode overlap efficiency and reduce coupling loss. This width setting method is a common parameter selection in the industry.

[0061] In embodiments of this disclosure, such as Figure 1 As shown, the first dielectric layer 1 is formed on the upper surface of the silicon substrate along the first direction; the first dielectric layer 1 and the second dielectric layer 2 are made of silicon oxide.

[0062] In other embodiments of this disclosure, a method for forming the fiber optic gyroscope integrated photonic chip provided in the above embodiments is also disclosed. Specifically, a first dielectric layer 1 is formed on a silicon substrate, and then a silicon nitride waveguide component 10 and a silicon nitride coupler 31 are formed in the first dielectric layer 1 by semiconductor integration process. Then, a second dielectric layer 2 is formed, and the lower structure is covered and planarized. A thin-film lithium tantalate waveguide 20 and a thin-film lithium tantalate coupler 32 are formed in the second dielectric layer 2, wherein the thin-film lithium tantalate coupler 32 and the silicon nitride coupler 31 are arranged opposite to each other along a first direction and are aligned by projection along the first direction. Finally, a first ground electrode 51, a signal electrode 52 and a second ground electrode 53 are formed above the thin-film lithium tantalate waveguide 20 along the first direction to obtain an integrated photonic chip with end-face coupling, beam splitting and combining, polarization multiplexing and phase modulation capabilities.

[0063] It is understandable that all the processes used in this method are conventional and mature manufacturing processes in the field of semiconductor integrated photonic chip manufacturing. It can be mass-produced by relying on standardized commercial semiconductor wafer fabrication lines in the industry, without the need for customized special process equipment and non-standard process steps. It has excellent process compatibility, stable yield in mass production, and controllable cost.

[0064] In other embodiments of this disclosure, a connection method and working process for the fiber optic gyroscope integrated photonic chip disclosed in the above embodiments are also provided to further demonstrate that the present invention can be implemented at the system level. This embodiment is merely one of the preferred implementation methods and does not constitute a limitation on the scope of protection.

[0065] It provides a light source, a polarization-maintaining fiber sensing loop, a photodetector, and modulation / demodulation and closed-loop control circuitry.

[0066] An external light source is optically connected to the main silicon nitride waveguide 111 within the chip via a first end-face coupler 41. The two ends of the polarization-maintaining fiber sensing loop are optically connected to the first multimode interference coupler 112 and the third thin-film lithium tantalate coupler 323 via second end-face couplers 42 and third end-face couplers 43, respectively, so that the beam-splittered light within the chip forms interference channels in both forward and reverse propagation directions within the sensing loop. A photodetector is optically connected to the output of the fourth thin-film lithium tantalate coupler 324 via a fourth end-face coupler 44 to receive the interference output light signal formed by the chip's beam combining. The aforementioned end-face coupler 4 can employ an end-face mode conversion structure to adapt to the mode field of the external fiber.

[0067] The incident light from the light source is split at the first multimode interference coupler 112 and coupled to the port path connected to the sensitive ring after polarization state management by the polarization multiplexer 113. After the light propagates in opposite directions in the sensitive ring and returns to the chip, it is combined by the second multimode interference coupler 114 to form an interference output.

[0068] In the optical path segment where phase modulation is required, the silicon nitride branch waveguide 12 establishes a low-loss interconnect with the thin-film lithium tantalate coupler 32 in the second dielectric layer 2 through the silicon nitride coupler 31, allowing light to enter the modulation segment of the thin-film lithium tantalate waveguide 20; the modulation / demodulation and closed-loop control circuit applies driving signals to the first ground electrode 51, the signal electrode 52 and the second ground electrode 53, generating an electro-optic effect in the thin-film lithium tantalate waveguide 20, thereby introducing phase modulation into the propagating light and obtaining a modulated optical signal that meets the requirements of gyroscope demodulation.

[0069] The photodetector performs photoelectric conversion on the interference light output from the fourth end coupler 44 to obtain an electrical signal; the modulation and demodulation and closed-loop control circuit synchronously demodulates and filters the electrical signal to form an error signal, and adjusts the phase modulation drive according to the error signal to keep the interference working point in a predetermined linear working range, thereby outputting a gyroscope signal related to the input angular velocity.

[0070] In summary, the working process and operating principle of the fiber optic gyroscope integrated photonic chip detailed in the above embodiments of this disclosure are merely exemplary implementations of this disclosure and are not intended to limit the scope of protection of this disclosure. It is understood that those skilled in the art, without departing from the core design concept and optical principles of this disclosure, can flexibly adjust, equivalently replace, and adaptively optimize the optical path transmission sequence, signal modulation logic, interlayer coupling method, functional structure combination, and optical path topology architecture in the above working process according to different application scenarios and different integration requirements of fiber optic gyroscope products. Such adjustments and optimizations do not deviate from the core inventive concept of this disclosure and should all fall within the scope of protection of this disclosure.

[0071] It should be understood that the phrase "an embodiment" or "one embodiment" throughout the specification means that a specific feature, structure, or characteristic related to the embodiment is included in at least one embodiment of this disclosure. Therefore, "in one embodiment" or "one embodiment" appearing throughout the specification does not necessarily refer to the same embodiment. Furthermore, these specific features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. It should be understood that in the various embodiments of this disclosure, the sequence numbers of the above-described processes do not imply a sequential order of execution; the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this disclosure. The sequence numbers of the above-described embodiments are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0072] The methods disclosed in the several method embodiments provided in this disclosure can be arbitrarily combined without conflict to obtain new method embodiments.

[0073] The above are merely specific embodiments of this disclosure, but the scope of protection of this disclosure is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this disclosure should be included within the scope of protection of this disclosure.

Claims

1. A fiber optic gyroscope integrated photonic chip, characterized in that, include: A first dielectric layer (1) and a second dielectric layer (2) are stacked sequentially along a first direction; the first direction is perpendicular to the plane in which the first dielectric layer (1) is located; A silicon nitride waveguide assembly (10) and a silicon nitride coupler (31) are formed in the first dielectric layer (1), and the silicon nitride coupler (31) is connected to the silicon nitride waveguide assembly (10); A thin-film lithium tantalate waveguide (20) and a thin-film lithium tantalate coupler (32) are formed within the second dielectric layer (2); the thin-film lithium tantalate coupler (32) is connected to the thin-film lithium tantalate waveguide (20); The silicon nitride coupler and the thin-film lithium tantalate coupler are aligned by projection along a first direction, and the silicon nitride coupler (31) is coupled to the thin-film lithium tantalate coupler (32).

2. A fiber optic gyroscope integrated photonic chip according to any one of claims 1, characterized in that, The silicon nitride waveguide assembly (10) includes an input silicon nitride waveguide assembly (11) and a silicon nitride branch waveguide (12); the input silicon nitride waveguide assembly (11) is connected to the silicon nitride branch waveguide (12), and the silicon nitride branch waveguide (12) is connected to the silicon nitride coupler (31).

3. The fiber optic gyroscope integrated photonic chip according to claim 2, characterized in that, The input silicon nitride waveguide assembly (11) includes a first multimode interference coupler (112), a polarization multiplexer (113), and a second multimode interference coupler (114) that are optically connected sequentially along the optical path transmission direction through the main silicon nitride waveguide (111); the second multimode interference coupler (114) is connected to the silicon nitride branch waveguide (12).

4. The fiber optic gyroscope integrated photonic chip according to claim 3, characterized in that, The silicon nitride coupler (31) includes a first silicon nitride coupler (311) and a second silicon nitride coupler (312); The silicon nitride branch waveguide (12) includes a first branch silicon nitride waveguide (121) and a second branch silicon nitride waveguide (122); one end of the first branch silicon nitride waveguide (121) is connected to the second multimode interference coupler (114), and the other end of the first branch silicon nitride waveguide (121) is connected to the first silicon nitride coupler (311); one end of the second branch silicon nitride waveguide (122) is connected to the second multimode interference coupler (114), and the other end of the second branch silicon nitride waveguide (122) is connected to the second silicon nitride coupler (312).

5. The fiber optic gyroscope integrated photonic chip according to claim 4, characterized in that, The thin-film lithium tantalate coupler (32) includes a first thin-film lithium tantalate coupler (321) and a second thin-film lithium tantalate coupler (322); the thin-film lithium tantalate waveguide (20) includes a first thin-film lithium tantalate waveguide (201) and a second thin-film lithium tantalate waveguide (202) arranged in parallel. One end of the first thin-film lithium tantalate waveguide (201) is connected to the first thin-film lithium tantalate coupler (321), and one end of the second thin-film lithium tantalate waveguide (202) is connected to the second thin-film lithium tantalate coupler (322). The first thin-film lithium tantalate coupler (321) and the first silicon nitride coupler (311) are arranged opposite to each other along the first direction and are coupled together, so that the first thin-film lithium tantalate waveguide (201) and the first branch silicon nitride waveguide (121) are coupled together. The second thin-film lithium tantalate coupler (322) and the second silicon nitride coupler (312) are arranged opposite to each other along the first direction and are coupled together, so that the second thin-film lithium tantalate waveguide (202) and the second branch silicon nitride waveguide (122) are coupled together.

6. The fiber optic gyroscope integrated photonic chip according to claim 5, characterized in that, The fiber optic gyroscope integrated photonic chip also includes an end-face coupler (4); there are multiple end-face couplers (4), which are respectively connected to the thin-film lithium tantalate waveguide (20) and the silicon nitride waveguide assembly (10), and are used to couple with external optical fibers or external optical paths.

7. The fiber optic gyroscope integrated photonic chip according to claim 6, characterized in that, The end face coupler (4) includes a first end face coupler (41), a second end face coupler (42), a third end face coupler (43) and a fourth end face coupler (44). The first end face coupler (41) and the second end face coupler (42) are respectively coupled to the first multimode interference coupler (112); The thin-film lithium tantalate coupler (32) further includes a third thin-film lithium tantalate coupler (323) and a fourth thin-film lithium tantalate coupler (324); the third thin-film lithium tantalate coupler (323) is connected to the other end of the first thin-film lithium tantalate waveguide (201), and the fourth thin-film lithium tantalate coupler (324) is connected to the other end of the second thin-film lithium tantalate waveguide (202); The third end face coupler (43) and the third thin-film lithium tantalate coupler (323) are coupled together, and the fourth end face coupler (44) and the fourth thin-film lithium tantalate coupler (324) are coupled together.

8. The fiber optic gyroscope integrated photonic chip according to claim 7, characterized in that, A first ground electrode (51) is provided along a first direction of the first thin-film lithium tantalate waveguide (201); a signal electrode (52) is provided along a first direction between the first thin-film lithium tantalate waveguide (201) and the second thin-film lithium tantalate waveguide (202); and a second ground electrode (53) is provided along a first direction of the second thin-film lithium tantalate waveguide (202).

9. The fiber optic gyroscope integrated photonic chip according to claim 1, characterized in that, The cross-sectional shape of the silicon nitride coupler is one or a combination of two of the following: tapered or rectangular. The cross-sectional shape of the thin-film lithium tantalate coupler is the same as that of the silicon nitride coupler.

10. A fiber optic gyroscope integrated photonic chip according to claim 1, characterized in that, The first dielectric layer (1) is formed on the upper surface of the silicon substrate (6) along the first direction; the first dielectric layer (1) and the second dielectric layer (2) are made of silicon oxide.

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