Miniaturized interference integrated photon gyroscope

Abstract

A miniaturized interference integrated photonic gyroscope structure with top, middle and bottom silicon oxides deposited on a silicon substrate includes a broadband optical source or a semiconductor optical amplifier with a silicon nitride ring resonator wavelength filter, the silicon nitride ring resonator wavelength filter is connected with the thin film lithium niobate or piezoelectric actuation silicon nitride phase modulator, and the thin film lithium niobate or piezoelectric actuation silicon nitride phase modulator is vertically coupled with the silicon nitride waveguide spiral ring. A silicon nitride waveguide spiral ring is patterned on the thin bottom oxide layer and connected to the germanium detector by photonic wire bonding or by vertical integration of a mirror embedded into the silicon wafer with an air trench beneath the silicon nitride waveguide spiral ring. Various methods of coupling alternative materials are described, as well as the potential to connect several helical waveguides in gyroscope applications for enhanced sensitivity.

Description

[0001] Cross-references

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 351,894, filed on June 14, 2022, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The technology generally involves miniaturized interferometric integrated photonic gyroscopes. Background Art

[0004] As remote controlled and autonomous vehicles such as drones become more common, there is growing interest in gyroscopes as sensors for measuring angular velocity. One type of gyroscope in the field of measuring angular velocity is the integrated photonic gyroscope, in which the effect of rotation on an optical signal is monitored to detect the rotational velocity of the device. In such devices, the phase shift of light due to the Sagnac effect is used to measure angular velocity. Since there are no moving parts, there are inherent reliability advantages expected from such devices compared to competing technologies.

[0005] Optical gyroscopes, such as optical (fiber) gyroscopes based on optical ring resonators, use optical elements such as lasers, beam splitters, polarizers, phase modulators, circulators, resonators, and photodetectors. In order to provide accurate measurements, the various optical elements need to be accurately and stably aligned. In some cases, this may require bulky mechanical supports in order to accurately and reliably align the different optical elements.

[0006] Optical gyroscopes also require electrical or electronic components such as wave generators, lock-in amplifiers, FPGAs, and computer-implemented devices. These components can be bulky, and the size of the different optical and electrical components limits how small a gyroscope can be made. However, for many applications such as drones, a smaller gyroscope may be preferred (or necessary). All components (both optical and electrical / electronic) also require electrical connections between the components.

[0007] Advances in inertial measurement systems are still expected. Summary of the invention

[0008] An object of the present technology is to improve at least some of the inconveniences existing in the prior art, or to provide a method for enhancing the performance of a device.

[0009] It should be understood that at least some of the elements described herein can be manufactured by deposition. As described herein, chemical vapor deposition techniques or physical deposition techniques of various layers on substrates and other layers and other deposition techniques (such as layer bonding) provide non-removable attachment of layers to substrates and other layers, respectively.

[0010] As used herein, the term "deposition" in relation to a manufacturing method broadly refers to methods and processes for mechanically and / or chemically applying a material to one or more desired locations on a surface or as a layer, and patterning or removing selected areas of a deposited film. Methods and processes encompassed by the term "deposition" herein include, but are not limited to, spin coating, photoresist development and etching, photolithography, electron beam lithography, thermal oxidation, plasma etching, wet etching, electron beam deposition, low pressure chemical vapor deposition, plasma enhanced chemical vapor deposition, and physical vapor deposition.

[0011] The amounts or values ​​recited herein are intended to refer to the actual given values. The term "about" is used herein to refer to the approximation of such given values ​​that is reasonably inferred based on ordinary skill in the art, including equivalents and approximations resulting from experimental and / or measurement conditions for such given values.

[0012] According to a non-limiting embodiment of the present technology, an integrated photonic gyroscope is provided, which includes: a light source; a wavelength filter optically connected to the light source; at least one interference spiral ring optically connected to the wavelength filter, the interference spiral ring being formed of silicon nitride; and a detector optically connected to the interference spiral ring for receiving light from the interference spiral ring.

[0013] In some embodiments, the wavelength filter includes at least one ring resonator filter formed from silicon nitride.

[0014] In some embodiments, the integrated photonic gyroscope further includes a phase modulator optically connected between the at least one interferometric spiral ring and the detector.

[0015] In some embodiments, the integrated photonic gyroscope further includes a phase modulator optically connected between the wavelength filter and the at least one interferometer spiral ring.

[0016] In some embodiments, the integrated photonic gyroscope further includes a substrate; and at least one wavelength filter is formed in a first material layer disposed on the substrate, and a phase modulator is formed in a second material layer disposed parallel to the first layer.

[0017] In some embodiments, the integrated photonic gyroscope further includes a substrate; and at least one wavelength filter and a phase modulator are formed in a material layer connected to the substrate.

[0018] In some embodiments, the phase modulator is at least one thin film lithium niobate waveguide (TFLN) phase modulator; and at least one TFLN phase modulator includes: at least one lithium niobate waveguide; and a plurality of metal electrodes, wherein the plurality of metal electrodes are arranged adjacent to the at least one lithium niobate waveguide.

[0019] In some embodiments, the phase modulator is at least one SiN / PZT phase modulator; and the at least one SiN / PZT phase modulator comprises: a silicon nitride waveguide; and an electrode comprising lead zirconate titanate (PZT), the electrode being horizontally displaced from the waveguide.

[0020] In some embodiments, the integrated photonic gyroscope further includes at least one photonic wire bond connecting the waveguide to the detector.

[0021] In some embodiments, the integrated photonic gyroscope further includes a waveguide formed of thin film lithium niobate (TFLN) and a germanium detector formed on the silicon substrate.

[0022] In some embodiments, the integrated photonic gyroscope further includes a plurality of horizontally straight and tapered evanescent field vertical couplers, and the evanescent coupling occurs between the vertically disposed dissimilar silicon nitride waveguide and the silicon waveguide.

[0023] In some embodiments, the integrated photonic gyroscope also includes a vertical coupling region, which includes: a silicon nitride straight waveguide having a width of about 0.5um and a thickness of about 100nm after tapering; a silicon waveguide having a width of about 500nm and a thickness of about 220nm; and a vertical spacing between the silicon nitride straight waveguide and the silicon waveguide, the vertical spacing being: about 1.95um for 10% coupling, 0.88um for 50% coupling, and 0.18um for 97% coupling.

[0024] In some embodiments, the integrated photonic gyroscope further includes a plurality of horizontally straight and tapered evanescent field vertical couplers, and the evanescent coupling occurs between the vertically disposed dissimilar silicon nitride waveguide and lithium niobate waveguide.

[0025] In some embodiments, the integrated photonic gyroscope also includes a vertical coupling region, which includes: a silicon nitride straight waveguide having a width of about 2.8um and a thickness of about 100nm; a lithium niobate waveguide having a width of about 1.5um and a thickness of about 100nm; and a vertical spacing between the silicon nitride straight waveguide and the lithium niobate waveguide, which is about 0.825um for 99.97% coupling.

[0026] In some embodiments, the integrated photonic gyroscope further includes a mirror formed of silicon that provides optical coupling between the at least one interferometric spiral ring and the at least one detector.

[0027] In some embodiments, the integrated photonic gyroscope further comprises at least one vertical coupler; and a plurality of etched cavities defined in the material below the at least one interference spiral ring, none of the plurality of etched cavities being defined in a region immediately below a coupling region defined around the at least one vertical coupler.

[0028] In some embodiments, the light source includes at least one of: a distributed feedback (DFB) laser; a superluminescent diode (SLD) source; and an amplified spontaneous emission (ASE) source.

[0029] In some embodiments, the light source includes a semiconductor optical amplifier (SOA).

[0030] According to some non-limiting examples of the present technology, an integrated photonic gyroscope is provided, which includes: a semiconductor optical amplifier (SOA); at least one interference spiral ring optically connected to a wavelength filter, at least one interference spiral ring formed of silicon nitride; and a detector optically connected to the interference spiral ring for receiving light from the interference spiral ring.

[0031] The embodiments of the present disclosure each have at least one of the above-mentioned purposes and / or aspects, but do not necessarily have all of the above-mentioned purposes and / or aspects. It should be understood that some aspects of the present disclosure generated by attempting to obtain the above-mentioned purposes may not meet the purposes and / or may meet other purposes not specifically described herein.

[0032] Additional and / or alternative features, aspects, and advantages of embodiments of the present disclosure will become apparent from the following description, drawings, and appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] For a better understanding of the present technology and other aspects and further features thereof, reference is made to the following description to be used in conjunction with the accompanying drawings, in which:

[0034] Figure 1 is a perspective schematic diagram of a non-limiting embodiment of a miniaturized interferometric integrated photonic gyroscope, wherein a phase modulator is disposed between the helical ring and the detector, and the beam propagates in a clockwise or counterclockwise direction;

[0035] Figure 2 yes Figure 1 A cross-sectional view of a miniaturized interferometric fiber optic gyroscope;

[0036] Figure 3 is a perspective schematic diagram of another non-limiting embodiment of a miniaturized interferometric integrated photonic gyroscope, wherein a thin film lithium niobate (TFLN) phase modulator is placed between a light source and a spiral ring, and its light beam propagates in a clockwise or counterclockwise direction during use;

[0037] Figure 4 yes Figure 3 Cross-sectional view of the miniaturized interferometric integrated photonic gyroscope;

[0038] Figure 4(a) is a perspective schematic diagram of another non-limiting embodiment of a miniaturized interferometric integrated photonic gyroscope, wherein during use the beam propagates in both clockwise and counterclockwise directions;

[0039] Figure 5 is a perspective schematic diagram of another non-limiting embodiment of a miniaturized interferometric integrated photonic gyroscope having an evanescent field vertical coupler;

[0040] Figure 6 yes Figure 5 Simulation of the coupling between two vertical couplers;

[0041] Figure 7 yes Figure 3 Simulation of the coupling between two vertical couplers;

[0042] Figure 8 is a perspective schematic diagram of four spiral rings connected by a silicon nitride tapered waveguide evanescent field vertical coupler;

[0043] Fig. 9 is a perspective schematic diagram of an evanescent field vertical coupler, in which evanescent coupling occurs between two vertically placed silicon nitride waveguides;

[0044] Fig.10 yes Fig. 9 Simulation of the coupling between two vertical couplers;

[0045] Fig.11 It is a simulation of the minimum rotation and helical length for a silicon nitride waveguide propagation loss of 0.5 dB / m, including shot noise and thermal noise, and the total noise which is the sum of shot noise and thermal noise;

[0046] Fig.12 It is a simulation of the minimum rotation and helical length for a silicon nitride waveguide propagation loss of 3dB / m, including shot noise and thermal noise, and the total noise which is the sum of shot noise and thermal noise;

[0047] Fig.13 is a perspective schematic diagram of a spiral ring with waveguide crossings such that all waveguide crossings are perpendicular to reduce crosstalk;

[0048] Fig.14 yes Fig.13 The simulation of the remaining power in the output waveguide after the spiral propagates from point A to point B by making seven waveguides cross;

[0049] Fig.15 is a perspective schematic diagram of a spiral ring, wherein the silicon below the waveguide in the region (area) enclosed between the dashed lines will be etched;

[0050] Fig.16is a perspective schematic diagram of a spiral ring, wherein a reflector is constructed at the center of the spiral ring to reflect the beam in a vertical direction to a detector;

[0051] Fig.17 yes Fig.16 a cross-sectional view of the structure; and

[0052] Fig.18 is a perspective cross-sectional view of a PZT phase modulator having a U-shaped PZT material.

[0053] It should be understood that throughout the drawings and corresponding descriptions, like features are identified by like reference numerals. Furthermore, it should also be understood that the drawings and subsequent descriptions are intended for illustrative purposes only, and such disclosure does not provide limitations on the scope of the claims. It should be noted that the drawings may not be drawn to scale unless otherwise noted. DETAILED DESCRIPTION

[0054] The present disclosure is directed to systems, methods, and apparatus for addressing deficiencies of the prior art.

[0055] The Sagnac effect is used to determine the phase difference in gyroscopes of the type described in this article. The phase difference between two counter-propagating waves is accumulated over a long optical waveguide coil (also called a loop) in order to obtain high responsivity with a compact device. For an ideal integrated optical waveguide and components, the output photogenerated current I can be described by the following expression:

[0056]

[0057] I0=σP / 2, Equation (3)

[0058] in, is the so-called Sagnac phase shift, σ is the photodetector responsivity, and P is the power coupled into the input integrated optical waveguide.

[0059] Sagnac Phase Shift is the phase shift difference between two counter-propagating waves along the same optical path and is described by the following expression:

[0060]

[0061] Wherein, Ω is the angular velocity, λ is the vacuum wavelength, N is the number of loops of the integrated optical waveguide coil, D is the diameter of the integrated optical waveguide coil, and L is the length of the integrated optical waveguide coil.

[0062] Figure 1is a perspective schematic diagram of an interferometric integrated photonic gyroscope 101. The gyroscope 101 includes an interferometric sensing element or spiral, a phase modulator, a photodiode, a light source or laser diode, an isolation support element (e.g., a silicon oxide layer), all on a support wafer or substrate. The phase modulator is shown with an actuator electrode for electrical adjustment of the phase and can be made of lithium niobate with metal electrodes or silicon nitride with piezoelectric electrodes. The spiral includes a silicon nitride waveguide, which when surrounded by silicon oxide is used to confine the optical mode traveling in the waveguide.

[0063] In this embodiment, the phase modulator 190 is placed between the spiral ring 110 and the detector 315. The phase modulator 190 can be Figure 5 The thin film lithium niobate (TFLN) phase modulator shown in Fig.17 and Fig.18 The lead zirconate titanate (PZT) phase modulator shown in . See also, for example, “Ultra-low power stress-based phase actuation in TriPleX photonic circuits”, Everhardt et al., Proc. SPIE 12004, Integrated Optics: Devices, Materials, and Technologies XXVI, 1200405 (March 5, 2022), referred to herein as “Everhardt”, the entire contents of which are incorporated herein by reference.

[0064] Light from a broadband laser or semiconductor optical amplifier (SOA) 150 is launched into the input waveguide 130 of the spiral ring 110. In the case if the light source 150 is an SOA, it is externally coupled to a wavelength filter 140. In the case of a broadband laser, the wavelength filter 140 is not required. The wavelength filter 140 is made of a silicon nitride ring resonator utilizing the Vernier effect and is placed after the SOA 150 to further reduce the line width of the SOA 150. The light travels to the silicon nitride spiral ring input waveguide 130 to reach the spiral ring 110, which forms the sensing element of the gyroscope for measuring the Sagnac effect. In the coupling region 160, the output light from the center 120 of the spiral ring is vertically coupled to the input straight waveguide 170 or input tapered waveguide 171 of a thin film lithium niobate waveguide 180 placed between two metal electrodes 191 and 192 constituting a thin film lithium niobate (TFLN) phase modulator 190. Similarly, a SiN phase modulator actuated by a horizontally coupled PZT can be used. In the coupling region 160, the coupling waveguide can be a straight waveguide 170 or a straight waveguide 151 or a tapered waveguide 171 or a tapered waveguide 152, such as Figure 1As shown in and in more detail as Figure 5 As shown in . The silicon / germanium detector 315 is attached to the silicon substrate 335. The output light from the phase modulator is coupled into the silicon / germanium detector 315 via the photon wire bond 114, which is fabricated using direct write 3D laser lithography based on two-photon polymerization. The detector 315 is first fixed on the silicon substrate 335, and then the interconnection area between the lithium niobate waveguide 180 and the detector 315 is embedded in the photosensitive polymer. Two-photon lithography is then used to design the shape of the photon wire bond waveguide. Layers 111, 112 and 113 form the top layer, buffer layer and bottom layer of the waveguide 101, which are formed on the silicon substrate 335. The silicon nitride ring 110 is patterned on the bottom oxide layer 113.

[0065] In some embodiments, light source 150 may be replaced by a SLD or ASE broadband source to minimize backscattering noise in helical ring 110. The SLD or ASE broadband source may have an operating wavelength of about 1310 nm or 1550 nm.

[0066] In another embodiment, the positions of the laser and SOA and wavelength filter may be interchanged with the position of the detector.

[0067] Figure 2 yes Figure 1 A cross-sectional view of a miniaturized interferometric integrated photonic gyroscope is provided, providing additional illustration of the phase modulator 190 disposed between the helical ring 110 and the detector 315.

[0068] Figure 3 301 is a perspective schematic diagram of a miniaturized interferometric integrated photonic gyroscope, wherein a phase modulator 390 is placed between a light source (laser or SOA) 350 and a spiral ring 310. The phase modulator 390 may be, for example, Figure 5 The thin film lithium niobate (TFLN) phase modulator shown in Fig.17 and Fig.18 And also the SiN / PZT phase modulator shown in Everhardt.

[0069] Light from a light source 350 is emitted into the center 320 of a spiral ring 310 made of a silicon nitride waveguide. In the case where 350 is an SOA, it is externally coupled to a wavelength filter 340. In the case of a broadband laser, the wavelength filter 340 is not required. The wavelength filter 340 is made of a silicon nitride ring resonator using a vernier effect and is placed after the SOA 350 to further reduce the line width of the SOA 350. The output of the waveguide filter 340 made of silicon nitride is coupled to a lithium niobate waveguide 380 through a point converter not shown in the figure, and is placed between two metal electrodes 391 and 392 constituting a thin film lithium niobate (TFLN) phase modulator 390. In the coupling region 360, the coupling waveguide may be a straight waveguide 370 or a straight waveguide 351 or a tapered waveguide 371 or a tapered waveguide 352, such as Figure 1 or in more detail as shown in Figure 5 . The modulated light is coupled down to the center 320 of the spiral ring 310, which forms the sensing element of the gyroscope for measuring the Sagnac effect, either through a straight waveguide 370 or through a horizontally tapered vertical coupler 371 via a coupling region 360. Light from the output waveguide 330 of the spiral ring 310 is coupled into the silicon / germanium detector 315 in the coupling region 355. In the coupling region 355, the silicon nitride waveguide has been tapered to a linear waveguide with a width of 1.5um to match the effective refractive index with the effective refractive index of the silicon waveguide 365. The silicon / germanium detector 315 is fabricated on or attached to silicon 325. In the embodiment shown, the silicon layer 325 supports the spiral ring 310, and the output of the spiral ring 330 has a plurality of air trenches 375 (also referred to as etched cavities) formed in the spiral ring. It should be noted that the air gap 375 shown in the figure only represents the region 375 in which many air trenches are formed. For additional information regarding the formation and effects of air cavities, see also U.S. Patent Application No. 18 / 110,989, filed on February 17, 2023, the entire contents of which are incorporated herein by reference. There is a thin oxide layer 313 between the silicon nitride spiral ring 310 and the air cavity 375.

[0070] Figure 4 yes Figure 3 A cross-sectional view 401 of a miniaturized interferometric integrated photonic gyroscope is shown, wherein the phase modulator 390 is placed between the wavelength filter 340 and the spiral ring 310. Figure 4 In the Figure 3 The remain the same.

[0071] Figure 4(a) is a perspective schematic diagram 401a of a miniaturized interferometric integrated photonic gyroscope, in which beams propagate in clockwise and counterclockwise directions. In the figure, a laser, a three-port coupler also used as a circulator, and a spiral ring are placed in a first material layer, and two two-phase modules, each consisting of a thin film lithium niobate and two metal electrodes, are arranged in a second material layer parallel to the first material layer. The arrows in the figure show the direction of vertical coupling from silicon nitride to thin film lithium niobate, and vice versa. The clockwise beam and the counterclockwise beam are combined through the three-port coupler to form an interference beam. When there is no rotation, there is no Sagnac phase shift, and when there is rotation, a Sagnac phase shift occurs.

[0072] Figure 5 is a perspective schematic diagram of an evanescent field vertical coupler 501, wherein evanescent coupling occurs between two vertically placed silicon nitride waveguides and a lithium niobate waveguide in a coupling region 570 or 580. The coupling region 570 may have a coupled silicon nitride straight waveguide 5211 and a lithium niobate straight waveguide 5221 or a tapered silicon nitride straight waveguide 521 and a tapered lithium niobate waveguide 522. In a similar manner, the coupling region 580 may have a coupled silicon nitride straight waveguide 5231 and a lithium niobate straight waveguide 5241 or a tapered lithium niobate straight waveguide 523 and a tapered silicon nitride waveguide 524. Light from the lower silicon nitride waveguide 521 or 5211 is vertically coupled to the upper lithium niobate waveguide 522 or 5221 in the vertical coupling region 570 by vertical evanescent coupling. The power coupled to the waveguide 530 can be varied by changing the vertical gap between the waveguide 510 and the waveguide 530 and also by changing the length of the overlap region between the waveguide 5211 and the waveguide 5221 or between the waveguide 521 and the waveguide 522. In a similar manner, light can be coupled back from the upper lithium niobate waveguide 530 to the lower silicon nitride waveguide 520 in the vertical coupling region 580 by vertical evanescent coupling. The advantage of the silicon nitride waveguide and the lithium niobate tapered waveguide in the coupling region 570 and the coupling region 580 is to provide efficient vertical coupling with a much smaller coupling length. The input waveguide 510 and the output waveguide 520 are patterned on the silicon oxide layer 513, while the lithium niobate waveguide 530 is patterned on the silicon oxide layer 512. The surface-to-surface gap between the upper lithium niobate waveguide 530 and the lower silicon nitride input waveguide 510 and the lower silicon nitride output waveguide 520 can be varied to adjust the maximum vertical coupling efficiency. The light beam propagating in the thin film lithium niobate waveguide (TFLN) 530 is phase modulated by two electrodes 541 and 542 placed adjacent to the TFLN waveguide 530, and the phase modulated light beam exits through the output waveguide 520. Layers 511, 512, and 513 form the top layer, buffer layer, and bottom layer of the waveguide 105, which are formed on a silicon substrate 535.

[0073] Figure 6 Shows the Figure 5 601 shows the simulation results of the vertical power coupled from the input lower silicon nitride straight waveguide 510 to the output upper lithium niobate straight waveguide 530 in the coupling region 570 of FIG. As can be seen from the figure, for a silicon nitride waveguide with a width of 2.8um and a thickness of 100nm and for a lithium niobate waveguide with a width of 1.5um and a thickness of 100nm, when the surface-to-surface gap between the two vertical waveguides is 0.825um and the coupling length is 9.6um, the remaining output power in the input silicon nitride waveguide 510 is 0.00035, or the power coupled to the output vertical lithium niobate waveguide 530 is 0.9997 or 99.97%. Similarly, in Figure 5 The vertical power coupled from the upper lithium niobate waveguide 530 to the lower silicon nitride waveguide 520 in the coupling region 580 of is 99.97%.For this simulation, the refractive index of silicon nitride was chosen to be 2.08, and for lithium niobate it was chosen to be 2.2.

[0074] Figure 7 The coupling from the silicon nitride waveguide 345 to the Figure 3 701 shows the simulation results of the vertical power of the silicon waveguide 365 attached to the detector 315. The vertical coupling occurs as Figure 3 In the coupling region 355 shown in FIG. Figure 7 ,when Figure 3 When the vertical gap between the upper surface of the silicon waveguide 365 and the lower surface of the silicon nitride waveguide 345 is 0.18 um, about 97% of the light is coupled to Figure 3 On the other hand, when the vertical gap between the upper surface of the silicon waveguide 365 and the lower surface of the silicon nitride waveguide 345 increases to 2.38um, then the coupled light drops to 7.7%. However, for a typical vertical gap of 1.95um, about 9.3% of the light is coupled from the silicon nitride waveguide 345 to the silicon waveguide 365. Simulations have been performed for a tapered single-mode silicon nitride waveguide 345 with a width of 0.5um and a thickness of 100nm, and for a standard single-mode silicon waveguide 365 recommended by the foundry with a width of 0.5um and a thickness of 0.22um.

[0075] Figure 8 is a via on a separate die as shown by dashed line 815 and dashed line 816 and also in Fig. 9 801 is a perspective view of four spiral rings connected by a bi-silicon nitride waveguide evanescent field vertical coupler. In some embodiments, the four spiral rings can be implemented to replace Figure 1 and Figure 3 The increased loop length is beyond what can be achieved on one die for increased sensitivity. Figure 8 , the four spiral rings consist of Figure 1 and Figure 3 The single spiral ring formation, however, represents a method for connecting four adjacent dies for increased ring area and enhanced sensitivity. Fig.12 It is shown that for a high loss waveguide with 3 dB loss per meter, there is no benefit to increasing the silicon nitride waveguide length, but for Fig.11 The low-loss silicon nitride waveguides shown here show some benefits.

[0076] Reference Figure 8 , indicating a method of increasing gyroscope sensitivity for increasing the maximum spiral length achievable on the area of ​​one die by bridging several dies together when the waveguide losses are low enough. All spirals must be wound in the same direction to enhance the Sagnac effect. The input silicon nitride waveguide 810, the output silicon nitride waveguide 820, and rings 1 (821), 2 (822), 3 (823), and 4 (824) are first-level silicon nitride (as shown by the solid lines) and are patterned on silicon oxide 830, while the vertical couplers 815 and 816 are second-level silicon nitride (as shown by the dotted lines) and are patterned on an intermediate layer of silicon oxide with a thickness of 1.95um. The bridged nitride layer crosses the cut line and can be formed in one step by a photolithography process, or by splicing or lithography when necessary.

[0077] Reference Figure 8 , light from laser 810 is emitted into ring 1 (821), and is coupled vertically upward to silicon nitride vertical coupler 815 via coupling region 841, and then vertically coupled downward to ring 2 (822) via coupling region 842. Light from ring 2 (822) propagates to ring 3 (823) via connecting waveguide (817). Light from ring 3 (823) is vertically coupled to vertical coupler 816 via coupling region 843, to ring 4 (824), and then vertically coupled downward to ring 4 (824) via coupling region 844 and exits through output waveguide 820. The amount of light coupled in coupling region 841, coupling region 842, coupling region 843, and coupling region 844 is about 1.38 W. Fig.10 46 and described in paragraph 46.

[0078] Fig. 9is a perspective schematic diagram of an evanescent field vertical coupler 901, in which evanescent coupling occurs between two vertically placed silicon nitride waveguides in a coupling region 970 or 980. The coupling region 970 may have coupled silicon nitride straight waveguides 9211 and 9221 or tapered silicon nitride straight waveguides 921 and 922. In a similar manner, the coupling region 980 may have coupled silicon nitride straight waveguides 9231 and 9241 or tapered silicon nitride straight waveguides 923 and 924. Light from the lower input silicon nitride waveguide 921 or 9211 is vertically coupled to the upper silicon nitride waveguide 922 or 9221 in the vertical coupling region 970 by vertical evanescent coupling. The power coupled to the waveguide 930 can be varied by changing the vertical gap between the waveguide 910 and the waveguide 930 and also by changing the length of the overlap region between the waveguide 9211 and the waveguide 9221 or the waveguide 921 and the waveguide 922. In a similar manner, light can be coupled from the upper silicon nitride waveguide 930 back to the lower silicon nitride waveguide 920 in the vertical coupling region 980 by vertical evanescent coupling. The advantage of the silicon nitride tapered waveguides in the coupling region 970 and the coupling region 980 is to provide efficient vertical coupling with a much smaller coupling length. The input waveguide 910 and the output waveguide 920 are patterned on the silicon oxide layer 913, while the silicon nitride waveguide 930 is patterned on the silicon oxide 912. The surface-to-surface gap between the upper silicon nitride waveguide 930 and the lower silicon nitride input waveguide 910 and the lower silicon nitride output waveguide 920 can be varied to adjust the maximum vertical coupling efficiency. Layers 911, 912, and 913 form the top, buffer, and bottom layers of the waveguide 901, which are formed on a silicon substrate 935.

[0079] Fig.10 Shows the Fig. 9 1011 shows the simulation results of the vertical power coupled from the lower silicon nitride straight waveguide 910 to the upper silicon nitride straight waveguide 930 in the coupling region 970 and the coupling region 980. As can be seen from the figure, for a silicon nitride waveguide with a width of 2.8um and a thickness of 100nm, when the surface-to-surface gap between the two vertical waveguides is 1.95um and the coupling length is 150um, the residual power in the input silicon nitride waveguide 910 is 0.0064, or the power coupled to the output vertical waveguide 930 is 0.9944 or 99.34%. Similarly, in the same Figure 5 The vertical power coupled from the upper silicon nitride waveguide 930 to the lower silicon nitride waveguide 920 in the coupling region 980 is 99.34%. The refractive index of silicon nitride was chosen to be 2.08 for this simulation.

[0080] Fig.11A graph 1111 of minimum rotation (degrees / hour / square (Hz)) versus spiral length (meters) for two types of noise (i.e., shot noise and thermal noise) is shown when the propagation loss of the spiral ring is 0.5 dB / km at a wavelength of 1550 nm. Both noises have optimal values ​​when plotted as spiral length. For a source input power of 100 mW and a spiral ring length of 22.2721 meters, the number of rings required to fit in a 2 cm×2 cm reticle is approximately 526 with the same silicon nitride waveguide of 28 um width and 100 nm thickness and 10 um surface-to-surface spiral waveguide spacing. The corresponding minimum rotations for shot noise and thermal noise are 0.28 (degrees / hour / square (Hz)) and 0.5 (degrees / hour / square (Hz)), and the total noise (sum of shot noise and thermal noise) is 0.78 (degrees / hour / square (Hz)).

[0081] However, as in Fig.12 As shown in FIG. 1211 , when the propagation loss of the spiral ring increases to 3 dB / km at a wavelength of 1550 nm, the spiral ring length decreases to 5.38875 meters, while the silicon nitride surface-to-surface spiral waveguide spacing remains at 10 um, for the same source input power of 100 mW and the corresponding smaller number of rings is 90. In this case, the corresponding minimum rotation for shot noise and thermal noise increases to 1.57 (degrees / hour / square (Hz)) and 1.59 (degrees / hour / square (Hz)), respectively, and the total noise (the sum of shot noise and thermal noise) increases to 3.16 (degrees / hour / square (Hz)).

[0082] For low loss silicon nitride waveguides, when propagation losses are of the order of 0.5 dB / meter at a wavelength of 1550 nm, simulations indicate that to obtain a total detector noise (sum of shot noise and thermal noise) rotation rate of 0.78 (degrees / hour / square (Hz)), in the case of a silicon nitride waveguide of 2.8 um width and 100 nm thickness and 10 um surface-to-surface waveguide spacing, a spiral length of about 22 meters is required that can fit in a reticle of size 2 cm x 2 cm. However, for a propagation loss of 0.1 dB / meter at a wavelength of 1550 nm, the spiral loop length becomes much greater than 22.2721 meters and may not fit into one reticle, and therefore multiple reticles are required. Figure 8 The geometry shown in is a method for achieving longer helices when warranted by a low-loss waveguide.

[0083] Fig.13 13 is a perspective schematic diagram of a spiral ring with waveguide crossing 1311. The spiral ring with waveguide crossing 1350 can be composed of Figure 1 and Figure 3 The single helical ring in is replaced. Fig.13The spiral ring 1350 does not need to come from Figure 1 , Figure 3 and Figure 5 , thereby simplifying fabrication. However, the spiral ring 1350 adds loss at each crossing, and twice, once for the input beam propagating from A to B, and again for the output beam propagating from B to C. Fig.13 , light from a laser source enters a silicon nitride ring 1350 via a silicon nitride input waveguide 1310 and exits through a silicon nitride output waveguide 1320. When propagating from A to B, the input beam will propagate through crossover 1347, crossover 1346, crossover 1345, crossover 1344, crossover 1343, crossover 1342, and crossover 1341, and when propagating from B to C, the output beam will propagate through crossover 1341, crossover 1342, crossover 1343, crossover 1344, crossover 1345, crossover 1346, and crossover 1347. The input waveguide 1310, the output waveguide 1320, and the ring 1350 are patterned on thermally grown silicon oxide 1330 on a silicon wafer 1360. Figure 5 , Fig.17 and Fig.18 The phase modulator can be placed just after the input waveguide 1310 or just before the output waveguide 1320.

[0084] Fig.14 The simulated loss 1411 is shown for when the output beam propagates from B to C. In this case, the beam will propagate through Fig.13 There are 7 waveguide crossovers similarly labeled 1341, 1342, 1343, 1344, 1345, 1346 and 1347. Fig.13 and Fig.14 , the power remaining in the output waveguide 1320 is about 0.87 or 87%, which means that about 13% power is lost when propagating through 7 crossovers, or 1.85% (0.06 dB) power is lost when propagating through each crossover. In the simulation, the silicon nitride waveguide thickness is considered to be 100 nm, while the width is kept at 2.8 um to support only the fundamental TE mode in the absence of higher order TE modes. Fig.13 The estimated waveguide crossing loss for 90 loops when propagating from A to B and then from B to C is estimated to be 10.8 dB (0.06 dB x 2 x 90). In all cases, the crossing must be perpendicular to the spiral loops, as any deviation from this will result in additional coupling between the crossing waveguides.

[0085] Fig.151511 is a perspective schematic diagram of a spiral ring 1550, wherein the silicon below the area (region) enclosed between the dashed lines 1560 will be selectively etched away. The spiral ring can be composed of a single spiral ring such as Figure 1 or Figure 3 The single helical ring shown in FIG. Fig.15 , light enters the silicon nitride spiral ring 1550 through the silicon nitride input waveguide 1510, and then leaves through the silicon nitride output waveguide 1520. The spiral ring 1550 can be composed of Fig.13 Medium or Figure 1 and Figure 3 The spiral ring 1350 in is replaced. Figure 5 , Fig.17 and Fig.18 The phase modulator can be placed just after the input waveguide 1510 or just before the output waveguide 1520. Fig.15 As shown in , the silicon below the area (region) enclosed between the dashed lines 1560 will be etched with XeF2 (xenon difluoride) to form a plurality of air cavities therein. For reference, see again US Patent Application No. 18 / 110,989.

[0086] Fig.16 1611 is a perspective schematic diagram of a spiral ring 1650, wherein a reflector 1690 is constructed at the center 1620 of the spiral ring to reflect the beam in a vertical direction 1640 to a detector 1680. The spiral ring 1650 can be composed of Figure 1 The single helical ring in is replaced by Fig.16 , light enters the silicon nitride spiral ring 1650 through the silicon nitride input waveguide 1610, then exits through the silicon nitride output waveguide 1620, and is vertically reflected by the mirror 1690 to be detected by the germanium detector 1680 defined on the top silicon oxide 1670. The input waveguide 1610, output waveguide 1620, and ring 1650 are patterned on thermally grown silicon oxide 1630 on a silicon wafer 1660. The mirror 1690 can be formed by crystal etching of silicon, or added to a trench etched in silicon dioxide, so that the reflection angle relative to the input beam and the output beam is between 45 degrees and 54.7 degrees. Figure 5 The phase modulator in can be placed immediately after the input waveguide 1610.

[0087] Fig.17is a perspective cross-sectional view 1711 of a SiN / PZT phase modulator with a PZT material 1720. The PZT material 1720 is sandwiched vertically between two metal electrodes 1710 and 1711 for electrical actuation. A single strip silicon nitride waveguide 1730 is patterned on a thermally grown bottom silicon oxide 1732, which in turn is formed on a silicon substrate 1735. Layer 1731 is a top oxide layer that separates the silicon nitride waveguide 1730 from the bottom electrode 1711 in such a way that the evanescent field of the fundamental TE mode is not attenuated by the bottom metal electrode 1711. The SiN / PZT phase modulator 1711 can be made of Figure 5 The lithium niobate phase modulator is replaced.

[0088] Fig.18 18 is a perspective cross-sectional view 1811 of a PZT phase modulator having a U-shaped PZT material 1820, and is also shown by a top view 1890. The U-shaped PZT material 1820 is sandwiched vertically between two metal electrodes 1810 and 1811. A single strip silicon nitride waveguide 1830 is patterned on a thermally grown bottom silicon oxide 1832, which in turn is formed on a silicon substrate 1835. Layer 1831 is a top oxide layer that separates the silicon nitride waveguide 1830 from the bottom electrode 1811 in such a way that the evanescent field of the fundamental TE mode is not attenuated by the bottom metal electrode 1811. The PZT phase modulator can be made of Figure 5 Lithium niobate phase modulator or Fig.17 The PZT modulator shown in FIG.

[0089] Modifications and improvements to the above-described embodiments of the present technology may become apparent to those skilled in the art.The foregoing description is intended to be illustrative rather than limiting.

Claims

1. An integrated photonic gyroscope, comprising: light source; a wavelength filter optically connected to the light source; at least one interference spiral ring, the at least one interference spiral ring optically connected to the wavelength filter, the at least one interference spiral ring formed of silicon nitride; as well as A detector is optically connected to the interference spiral ring for receiving light from the interference spiral ring.

2. The integrated photonic gyroscope according to claim 1, wherein: The wavelength filter includes at least one ring resonator filter formed from silicon nitride.

3. The integrated photonic gyroscope according to claim 1 or 2, further comprising: A phase modulator is optically connected between the at least one interferometric spiral ring and the detector.

4. The integrated photonic gyroscope according to claim 1 or 2, further comprising: A phase modulator is optically connected between the wavelength filter and the at least one interference spiral ring.

5. The integrated photonic gyroscope according to any one of claims 1 to 4, further comprising: substrate; as well as in: The at least one wavelength filter is formed in a first material layer disposed on the substrate, and The phase modulator is formed in a second material layer arranged parallel to the first layer.

6. The integrated photonic gyroscope according to any one of claims 1 to 4, further comprising: substrate; as well as in: The at least one wavelength filter and the phase modulator are formed in a material layer connected to the substrate.

7. The integrated photonic gyroscope according to claim 3 or 4, wherein: The phase modulator is at least one thin film lithium niobate waveguide (TFLN) phase modulator; and The at least one TFLN phase modulator comprises: at least one lithium niobate waveguide, and A plurality of metal electrodes are disposed adjacent to the at least one lithium niobate waveguide.

8. The integrated photonic gyroscope according to claim 3 or 4, wherein: The phase modulator is at least one SiN / PZT phase modulator; and The at least one SiN / PZT phase modulator comprises: Silicon nitride waveguides, and An electrode comprising lead zirconate titanate (PZT) is horizontally displaced from the waveguide.

9. An integrated photonic gyroscope according to any one of claims 1 to 8, further comprising at least one photonic wire bond connecting a waveguide to the detector.

10. The integrated photonic gyroscope according to any one of claims 1 to 9, further comprising: a waveguide formed of thin film lithium niobate (TFLN), and Germanium or silicon detectors which are added to a silicon substrate.

11. The integrated photonic gyroscope according to any one of claims 1 to 10, further comprising: a plurality of horizontally straight and tapered evanescent field vertical couplers, and Here, evanescent coupling occurs between vertically placed dissimilar silicon nitride waveguides and silicon waveguides.

12. The integrated photonic gyroscope according to claim 11, further comprising: A vertical coupling region, the vertical coupling region comprising: A silicon nitride straight waveguide having a width of about 0.5 um and a thickness of about 100 nm after tapering; a silicon waveguide having a width of about 500 nm and a thickness of about 220 nm; and A vertical spacing between the silicon nitride straight waveguide and the silicon waveguide, wherein: For 10% coupling, it is about 1.95um. 0.88um for 50% coupling, and 0.18um for 97% coupling.

13. The integrated photonic gyroscope according to any one of claims 1 to 12, further comprising: a plurality of horizontally straight and tapered evanescent field vertical couplers; as well as Here, evanescent coupling occurs between vertically placed dissimilar silicon nitride waveguide and lithium niobate waveguide.

14. The integrated photonic gyroscope according to claim 13, further comprising: A vertical coupling region, the vertical coupling region comprising: A silicon nitride straight waveguide having a width of about 2.8 um and a thickness of about 100 nm; a lithium niobate waveguide having a width of about 1.5 um and a thickness of about 100 nm; and The vertical spacing between the silicon nitride straight waveguide and the lithium niobate waveguide is about 0.825 um for 99.97% coupling.

15. The integrated photonic gyroscope according to any one of claims 1 to 14, further comprising: A mirror formed of silicon provides optical coupling between the at least one interferometric spiral ring and the at least one detector.

16. The integrated photonic gyroscope according to any one of claims 1 to 15, further comprising: at least one vertical coupler; as well as a plurality of etch cavities defined in the material below the at least one interference spiral ring, None of the plurality of etch cavities is defined in a region immediately below a coupling region defined around the at least one vertical coupler.

17. The integrated photonic gyroscope according to any one of claims 1 to 16, wherein: The light source includes at least one of the following: a superluminescent diode (SLD) source; and Amplified spontaneous emission (ASE) source.

18. The integrated photonic gyroscope according to any one of claims 1 to 16, wherein: The light source includes a semiconductor optical amplifier (SOA).

19. An integrated photonic gyroscope, comprising: Semiconductor optical amplifier (SOA); at least one interference spiral ring, the at least one interference spiral ring optically connected to the wavelength filter, the at least one interference spiral ring formed of silicon nitride; as well as A detector is optically connected to the interference spiral ring for receiving light from the interference spiral ring.

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