WO2024000936A1 - 光学陀螺双层SiN基集成驱动芯片 - Google Patents

光学陀螺双层SiN基集成驱动芯片 Download PDF

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WO2024000936A1
WO2024000936A1 PCT/CN2022/126598 CN2022126598W WO2024000936A1 WO 2024000936 A1 WO2024000936 A1 WO 2024000936A1 CN 2022126598 W CN2022126598 W CN 2022126598W WO 2024000936 A1 WO2024000936 A1 WO 2024000936A1
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sin
waveguide
coupler
layer
optical fiber
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PCT/CN2022/126598
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French (fr)
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吕海斌
李汉舟
焦峰
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深圳市奥斯诺工业有限公司
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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
    • G01C19/00—Gyroscopes; Turn-sensitive devices using vibrating masses; Turn-sensitive devices without moving masses; Measuring angular rate using gyroscopic effects
    • G01C19/58—Turn-sensitive devices without moving masses
    • G01C19/64—Gyrometers using the Sagnac effect, i.e. rotation-induced shifts between counter-rotating electromagnetic beams
    • G01C19/72—Gyrometers using the Sagnac effect, i.e. rotation-induced shifts between counter-rotating electromagnetic beams with counter-rotating light beams in a passive ring, e.g. fibre laser gyrometers
    • G01C19/721—Details
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/0136—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  for the control of polarisation, e.g. state of polarisation [SOP] control, polarisation scrambling, TE-TM mode conversion or separation
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B2006/12133—Functions
    • G02B2006/12147—Coupler

Definitions

  • the present invention relates to the technical fields of integrated optics and inertial sensing, and in particular to an optical gyroscope double-layer SiN-based integrated drive chip.
  • fiber optic gyroscopes As an angular velocity sensor, fiber optic gyroscopes have significant advantages over traditional mechanical gyroscopes in terms of measurement accuracy, sensitivity and reliability, and are widely used in positioning, attitude control and absolute direction measurement. According to the classification of measurement accuracy, high-precision fiber optic gyroscopes are mainly used in the fields of space technology, military applications and scientific research, while low-cost, medium and low-precision fiber optic gyroscopes have broad applications in many civilian fields such as car navigation, positioning and attitude control, and robots. Application scenarios.
  • Fiber optic gyroscopes are generally based on separate optical fiber devices to achieve the generation, modulation and detection of optical signals. Different optical fiber devices are spliced through pigtails to form a Sagnac interference optical loop, which inevitably produces parasitic reflections, increased insertion loss at the connection point, and interference. A series of problems such as environmentally sensitive polarization mismatch, all of which will reduce system performance to varying degrees. In addition, using a series of discrete fiber optic components will increase the size and weight of the system. In recent years, with the development of integrated photonics, researchers have proposed integrated optical gyroscopes to solve the above problems.
  • An integrated optical driver chip is formed by integrating all active and passive optical components required for optical gyroscopes on the same chip except the sensing coil.
  • the chip can be connected with a sensing coil (such as polarization-maintaining fiber or ultra-low-loss silicon nitride waveguide, etc.) to form an interference optical gyroscope, thereby greatly reducing the size, weight, power consumption and cost of the optical gyroscope, and can provide optical
  • a sensing coil such as polarization-maintaining fiber or ultra-low-loss silicon nitride waveguide, etc.
  • phase shifter for interference optical gyroscopes, stable phase modulation is an important guarantee for achieving high sensitivity and high accuracy extraction of Sagnac phase difference signals in the system, which requires the phase shifter to have high modulation responsiveness, modulation linearity and Performance features such as large modulation bandwidth.
  • the integrated phase shifter currently widely used in fiber optic gyroscope systems is mainly based on the electro-optical effect in bulk lithium niobate waveguides.
  • the traditional LiNbO waveguide based on the proton diffusion process has some shortcomings:
  • Silicon nitride as a CMOS-compatible material, can be processed with standard CMOS processes, and the lower refractive index contrast of SiN waveguides with silicon dioxide cladding reduces due to sidewall roughness, dispersion and interference with the waveguide. Sensitivity to dimensional changes resulting in waveguide loss, SiN's optically transparent window can cover the near-infrared and visible wavelength ranges, making it suitable for non-optical communications fields. Therefore, in recent years, the silicon nitride platform has become a common process platform for integrated optics. However, SiN has no second-order nonlinear effect (thereby lacking a linear electro-optical effect), the third-order nonlinear effect is weak, and does not support electron doping, so it cannot achieve efficient and fast electro-optical modulation.
  • Typical heterogeneous integrated materials include: ferroelectrics, such as lithium niobate thin films (LiNbO 3 ); compound semiconductors, such as aluminum-gallium-arsenic (AlGaAs) and aluminum-gallium-nitride (AlGaN) series; graphene and polymers wait. Therefore, using thin film deposition, epitaxial growth and wafer bonding technologies, active devices that cannot be realized or have insufficient performance in SiN materials can be realized through specific heterogeneous integration materials and integrated on a single SiN chip.
  • the heterogeneous integration of LiNbO thin films with SiN/Si photonic integration platforms has received widespread attention and research.
  • the heterogeneously integrated SiN/Si-LiNbO thin film material system combines the good scalability of the SiN/Si photonic platform with the excellent electro-optical modulation performance of LiNbO .
  • the implemented electro-optic modulation devices (such as electro-optic phase and intensity modulators) show the advantages of large modulation bandwidth, high modulation efficiency, low on-chip insertion loss and high linearity, and their performance levels are comparable to the best levels of other material integration platforms. , and can also overcome some traditional limitations.
  • the underlying SiN/Si waveguide not only enables low-loss optical routing across the entire chip, but also allows the integration of this electro-optical modulator with a full set of SiN/Si photonic components, making the proposed SiN/Si- LiNbO platform very Suitable for emerging applications. Therefore, integrated photonics based on heterogeneous integrated thin film electro-optical materials is becoming a hot field in current academic and industrial circles.
  • the technical problem to be solved by the embodiments of the present invention is to provide an optical gyroscope double-layer SiN-based integrated driver chip to improve its stability and accuracy, and is suitable for the wavelength bands available for fiber optic gyroscopes such as 830nm, 850nm, 1310nm and 1550nm.
  • an optical gyroscope double-layer SiN-based integrated driver chip which from top to bottom includes a SiO 2 upper cladding layer, a SiN upper layer, a SiO 2 middle layer, a SiN lower layer, an electro-optical material thin film layer, SiO 2 lower cladding layer, and Si substrate layer; the chip adopts the first implementation structure or the second implementation structure, wherein,
  • the first implementation structure of the chip includes a first optical fiber-SiN waveguide coupler, a second optical fiber-SiN waveguide coupler, a first 3dB beam splitter, a polarizer, and a second 3dB beam splitter implemented in the SiN upper layer.
  • the external light source is connected to one end of the first optical fiber-SiN waveguide coupler through the optical fiber; the external photodetector is connected to one end of the second optical fiber-SiN waveguide coupler through the optical fiber; the other end of the first optical fiber-SiN waveguide coupler is connected to the second optical fiber-SiN waveguide coupler.
  • the other end of the SiN waveguide coupler is connected to the two branches of the first 3dB beam splitter respectively; the base waveguide of the first 3dB beam splitter is connected to one end of the polarizer; the other end of the polarizer is connected to the second 3dB beam splitter.
  • the base waveguide of the device is connected to each other; the two branches of the second 3dB beam splitter are connected to one end of the waveguide taper on the first and second interlayer vertical couplers; a SiO 2 intermediate layer of a certain thickness is spaced between the first and second layers.
  • a SiO 2 intermediate layer of a certain thickness is spaced between the first and second layers.
  • the waveguide tapers of the first and second inter-layer vertical couplers Directly below the upper waveguide taper of the inter-layer vertical coupler are the waveguide tapers of the first and second inter-layer vertical couplers; one end of the waveguide taper of the first and second inter-layer vertical coupler is phase-shifted with the first and second inter-layer vertical couplers respectively.
  • phase shifter One end of the phase shifter is connected to one end; the other ends of the first and second phase shifters are connected to one end of the waveguide taper under the third and fourth interlayer vertical coupler respectively; a certain thickness of SiO 2 intermediate layer is separated between the third and fourth layers.
  • the waveguide tapers on the third and fourth inter-layer vertical couplers respectively one end of the waveguide taper on the third and fourth inter-layer vertical coupler is connected to the third and fourth optical fibers respectively -
  • One end of the SiN waveguide coupler is connected; the other ends of the third and fourth fiber-SiN waveguide couplers are connected to both ends of the external optical fiber ring respectively;
  • the second implementation structure of the chip includes a first optical fiber-SiN waveguide coupler, a second optical fiber-SiN waveguide coupler, a first 3dB beam splitter, a polarizer, a second 3dB beam splitter, and The waveguide taper on the first interlayer vertical coupler, the waveguide taper on the second interlayer vertical coupler; the waveguide taper on the first interlayer vertical coupler, the waveguide taper on the second interlayer vertical coupler implemented in the lower layer of SiN, The first phase shifter, the second phase shifter, the first optical fiber-SiN/electro-optical material hybrid waveguide coupler, the second optical fiber-SiN/electro-optical material hybrid waveguide coupler;
  • the external light source is connected to one end of the first optical fiber-SiN waveguide coupler through the optical fiber; the external photodetector is connected to one end of the second optical fiber-SiN waveguide coupler through the optical fiber; the other end of the first optical fiber-SiN waveguide coupler is connected to the second optical fiber-SiN waveguide coupler.
  • the other end of the SiN waveguide coupler is connected to the two branches of the first 3dB beam splitter respectively; the base waveguide of the first 3dB beam splitter is connected to one end of the polarizer; the other end of the polarizer is connected to the second 3dB beam splitter.
  • the base waveguide of the device is connected to each other; the two branches of the second 3dB beam splitter are connected to one end of the waveguide taper on the first and second interlayer vertical couplers; a SiO 2 intermediate layer of a certain thickness is spaced between the first and second layers.
  • a SiO 2 intermediate layer of a certain thickness is spaced between the first and second layers.
  • the waveguide tapers of the first and second inter-layer vertical couplers Directly below the upper waveguide taper of the inter-layer vertical coupler are the waveguide tapers of the first and second inter-layer vertical couplers; one end of the waveguide taper of the first and second inter-layer vertical coupler is phase-shifted with the first and second inter-layer vertical couplers respectively.
  • One end of the first and second phase shifters is connected to one end of the first and second optical fiber-SiN/electro-optical material hybrid waveguide couplers respectively; the first and second optical fiber-SiN/electro-optical material hybrid waveguides The other end of the coupler is connected to both ends of the external optical fiber ring.
  • the working band of the chip is one or more of 830nm, 850nm, 1310nm and 1550nm.
  • the SiO 2 upper cladding layer is also provided with a polysilicon layer for absorbing stray light in the chip structure.
  • the SiO 2 intermediate layer is located between the SiN upper layer and the SiN lower layer.
  • the fiber-SiN waveguide couplers all adopt an inversed taper structure to achieve mode field diameter matching between the waveguide and the polarization-maintaining fiber at the end face of the chip.
  • the fiber-SiN/electro-optical material hybrid waveguide couplers all adopt an inversed taper structure to achieve mode field diameter matching between the hybrid waveguide and the polarization-maintaining fiber at the chip end face.
  • the 3dB beam splitter is implemented using a Y-shaped beam splitter or a 1 ⁇ 2 multi-mode interferometer beam splitter.
  • the polarizer is implemented using a fixed bending radius or a curved waveguide structure with continuous curvature.
  • interlayer vertical couplers adopt an upper and lower reverse taper structure to realize the coupling of light between the upper SiN waveguide and the lower SiN-electro-optical material hybrid waveguide.
  • first phase shifter and the second phase shifter utilize the linear electro-optical effect of the heterogeneous integrated thin-film electro-optical material to achieve phase modulation, which is achieved by using a hybrid SiN waveguide structure with a bottom-bonded electro-optical material thin film layer.
  • the optical gyroscope double-layer SiN-based integrated driver chip based on the electro-optical phase shifter of heterogeneous integrated thin-film electro-optical materials combines the good scalability of the SiN photonic platform and the excellent electro-optical modulation performance of the electro-optical material: the upper SiN waveguide can Low-loss optical transmission, splitting, and polarization are achieved on the entire chip, and the underlying electro-optical phase shifter can be integrated with a full set of SiN photonic components, making the proposed chip architecture very suitable for applications such as fiber optic gyroscopes.
  • thermo-optical coefficient of SiN material ensures that changes in ambient temperature have less impact on the optical transmission characteristics of the device, thereby suppressing the temperature drift effect and improving the stability of the gyroscope.
  • SiN material has high transmittance in the near-infrared wavelength region. Therefore, fiber optic gyroscopes based on SiN optical integrated chips can work in the short wavelength region and thus have a larger scale factor.
  • Figure 1 is a schematic diagram of the system composition of an optical gyroscope double-layer SiN-based integrated driver chip according to an embodiment of the present invention.
  • FIG. 2 is a perspective schematic diagram of the first implementation structure of the optical gyroscope double-layer SiN-based integrated driver chip according to the embodiment of the present invention.
  • FIG. 5 is an optical path diagram of the second implementation structure of the optical gyroscope double-layer SiN-based integrated driver chip according to the embodiment of the present invention.
  • Figure 6 is a schematic structural diagram of an interlayer vertical coupler according to an embodiment of the present invention.
  • Figure 8 is a schematic structural diagram of a phase shifter according to an embodiment of the present invention.
  • the hierarchical composition of the optical gyroscope double-layer SiN-based integrated driver chip according to the embodiment of the present invention is, from top to bottom, SiO2 upper cladding layer 2, SiN upper layer 3, SiO2 middle layer 4, SiN lower layer 5, electro-optical material thin film layer 6, SiO 2 Lower cladding layer 7, Si substrate layer 8.
  • the SiO 2 upper cladding layer 2 is also provided with a polysilicon layer 1 for absorbing stray light in the chip structure.
  • the system composition of the optical gyroscope double-layer SiN-based integrated driver chip according to the embodiment of the present invention is shown in Figure 1.
  • the first implementation structure of the optical gyro double-layer SiN-based integrated driver chip includes: a first optical fiber-SiN waveguide coupler 1-1, a second optical fiber-SiN waveguide coupler 1-2, first 3dB beam splitter 9, polarizer 10, second 3dB beam splitter 11, first interlayer vertical coupler 5-1, second interlayer vertical coupler 5-2, first phase shifter 6-1, second phase shifter 6-2, third interlayer vertical coupler 5-3, fourth interlayer vertical coupler 5-4, third fiber-SiN waveguide coupler 7-1, Quad fiber-SiN waveguide coupler 7-2.
  • the external light source is connected to one end of the first optical fiber-SiN waveguide coupler 1-1 through an optical fiber; the external photodetector is connected to one end of the second optical fiber-SiN waveguide coupler 1-2 through an optical fiber; the first optical fiber-SiN waveguide coupler 1- The other end of 1 and the other end of the second fiber-SiN waveguide coupler 1-2 are respectively connected to the two branches of the first 3dB beam splitter 9; the base waveguide of the first 3dB beam splitter 9 and the polarizer 10 One end is connected; the other end of the polarizer 10 is connected to the base waveguide of the second 3dB beam splitter 11; the two branches of the second 3dB beam splitter 11 are respectively connected to the waveguide taper and the upper waveguide taper of the first interlayer vertical coupler 5-1.
  • One end of the waveguide taper on the second interlayer vertical coupler 5-2 is connected; a SiO2 intermediate layer 4 is spaced with a certain thickness, the waveguide taper on the first interlayer vertical coupler 5-1, and the second interlayer vertical coupler 5-2 Directly below the upper waveguide taper are the lower waveguide taper of the first interlayer vertical coupler 5-1 and the lower waveguide taper of the second interlayer vertical coupler 5-2; the lower waveguide taper of the first interlayer vertical coupler 5-1, One end of the waveguide taper under the second interlayer vertical coupler 5-2 is connected to one end of the first phase shifter 6-1 and the second phase shifter 6-2 respectively; The other end of the shifter 6-2 is connected to one end of the lower waveguide taper of the third interlayer vertical coupler 5-3 and the lower waveguide taper of the fourth interlayer vertical coupler 5-4 respectively; there is a SiO2 intermediate layer 4 of a certain thickness, Directly above the lower waveguide taper of the third interlayer vertical coupler 5-3 and the lower
  • the light output from the external light source is coupled to the first optical fiber-SiN waveguide coupler 1-1 on the chip through the optical fiber in the direction marked by arrow 12.
  • the first optical fiber-SiN waveguide coupler 1-1 The output light contains two different polarization modes (quasi TE 0 and TM 0 ); after passing through the first 3dB beam splitter 9, the two different polarization modes enter the polarizer 10.
  • the Sagnac effect is generated, and the intensity of the interference light returned to the second 3dB beam splitter 11 along the above path changes; the interference light signal passes through the second 3dB beam splitter 11.
  • the polarizer 10, the first 3dB beam splitter 9, and the second fiber-SiN waveguide coupler 1-2 it is coupled and output to an external photodetector in the direction marked by arrow 13, thereby detecting the changing light intensity. After processing That is, the rotation angular velocity information is obtained.
  • the second implementation structure of the optical gyro double-layer SiN-based integrated driver chip includes: a first optical fiber-SiN waveguide coupler 1-1, a second optical fiber-SiN waveguide coupler 1-2, first 3dB beam splitter 9, polarizer 10, second 3dB beam splitter 11, first interlayer vertical coupler 5-1, second interlayer vertical coupler 5-2, first phase shifter 6-1, second phase shifter 6-2, first optical fiber-SiN/electro-optical material hybrid waveguide coupler 7-1, and second optical fiber-SiN/electro-optical material hybrid waveguide coupler 7-2.
  • One end of the waveguide taper on the second interlayer vertical coupler 5-2 is connected; a SiO2 intermediate layer 4 is spaced with a certain thickness, the waveguide taper on the first interlayer vertical coupler 5-1, and the second interlayer vertical coupler 5-2 Directly below the upper waveguide taper are the lower waveguide taper of the first interlayer vertical coupler 5-1 and the lower waveguide taper of the second interlayer vertical coupler 5-2; the lower waveguide taper of the first interlayer vertical coupler 5-1, One end of the waveguide taper under the second interlayer vertical coupler 5-2 is connected to one end of the first phase shifter 6-1 and the second phase shifter 6-2 respectively; The other end of the shifter 6-2 is connected to one end of the first optical fiber-SiN/electro-optical material hybrid waveguide coupler 7-1 and the second optical fiber-SiN/electro-optical material hybrid waveguide coupler 7-2 respectively; the first optical fiber-SiN The other ends of the SiN/electro-opti
  • the light output from the external light source is coupled to the first optical fiber-SiN waveguide coupler 1-1 on the chip through the optical fiber in the direction marked by arrow 12.
  • the first optical fiber-SiN waveguide coupler 1-1 The output light contains two different polarization modes (quasi TE 0 and TM 0 ); after passing through the first 3dB beam splitter 9, the two different polarization modes enter the polarizer 10.
  • the second phase shifter 6-2 After phase modulation by the second phase shifter 6-2, it is coupled into the fiber ring through the second fiber-SiN/electro-optical material hybrid waveguide coupler 7-2; the two beams of light travel clockwise and counterclockwise in the fiber ring respectively.
  • the two beams of light propagate in opposite directions in the clockwise direction, and the two beams of light satisfy the coherence condition.
  • the Sagnac effect is produced, and the intensity of the interference light returned to the second 3dB beam splitter 11 along the above path changes; the interference light signal passes through the second 3dB beam splitter 11.
  • the polarizer 10 After the polarizer 10, the first 3dB beam splitter 9, and the second optical fiber-SiN waveguide coupler 1-2, it is coupled and output to an external photodetector in the direction marked by arrow 13, thereby detecting the changing light intensity. After processing That is, the rotation angular velocity information is obtained.
  • the polarizer of the present invention adopts a polarizer based on a continuous curvature curved waveguide.
  • the optical fiber-SiN waveguide coupler adopts an inversed taper structure to achieve mode field matching between the SiN waveguide and the polarization-maintaining fiber at the end face.
  • mode field matching with the ultra-fine diameter polarization-maintaining fiber (cladding diameter is 40 ⁇ m, core diameter is 3 ⁇ m) can be achieved in the near-infrared band.
  • Coupling efficiency is greater than 90%.
  • the optical fiber-SiN/electro-optical material hybrid waveguide coupler adopts an inversedtaper structure to achieve mode field matching between the SiN-electro-optical material hybrid waveguide and the polarization-maintaining optical fiber at the end face.
  • mode field matching with ultra-fine diameter polarization-maintaining optical fiber (cladding diameter is 40 ⁇ m, core diameter is 3 ⁇ m) can be achieved in the near-infrared band. Coupling efficiency is greater than 90%.
  • the interlayer vertical coupler adopts an upper and lower reverse taper structure to realize the coupling of light between the upper SiN waveguide and the lower SiN-electro-optical material hybrid waveguide. Its structure is shown in Figure 6, and the design parameters include the above , the minimum width and length of the lower taper and the thickness of the middle SiO 2 layer.
  • the size of the upper SiN waveguide is 1200 ⁇ 45nm
  • the size of the lower mixed SiN-electro-optical material waveguide is 1200 ⁇ 100nm
  • the minimum width and length of the optimized upper taper are 250nm and 2.5um respectively
  • the minimum width of the lower taper is and length are 150nm and 2.5um respectively
  • the thickness of the middle SiO2 layer is 1um
  • the corresponding interlayer coupling efficiency is 95%.
  • the first 3dB beam splitter 9 and the second 3dB beam splitter 11 are implemented using Y-shaped beam splitters.
  • the transmittance of the quasi-TE 0 mode in the near-infrared band at each port is >49%.
  • the polarizer 10 is composed of a curved waveguide with continuously distributed curvature, and its structure is as shown in Figure 7 .
  • the waveguide lateral size, waveguide bending curvature distribution, and bending waveguide length it is possible to achieve: (1) The waveguide only supports two quasi-TE 0 /TM 0 modes, and there is a large enough gap between them.
  • the effective refractive index difference is different, so the bending radiation loss of TM 0 is much greater than TE 0 ; (2) The polarization extinction ratio between the two quasi-TE 0 /TM 0 modes is greater than 50dB, and the propagation loss of the quasi-TE 0 mode is less than 0.5dB ; (3) The curvature is continuously distributed from the input end to the output end to avoid the scattering loss caused by the discontinuous curvature in TE 0 mode.
  • the SiN waveguide size is 1200 ⁇ 45nm
  • the minimum bending radius is 500 ⁇ m
  • the total length of the curved waveguide is 5mm.
  • the phase shifter is implemented using a mixed SiN waveguide structure with a bottom-bonded electro-optical material layer; LiNO 3 crystal is selected as the thin-film electro-optical material, and its electro-optical coefficient r 33 is 30pm/V, and x-cut is used for crystal cutting. or y-cut scheme.
  • the structural design of the phase shifter is shown in Figure 8.
  • the thin film electro-optical material is bonded at the bottom of the SiN waveguide and a push-pull structure is used.
  • the phase shifter includes SiO cladding , metal electrodes and SiN waveguides, thin film electro-optical materials, SiO cladding , and Si substrate.
  • the modulation efficiency of the phase shifter is maximized and the waveguide transmission loss is minimized.
  • the mixed SiN-LiNO waveguide size is 1200 ⁇ 100 nm
  • the thickness of the LiNO film is 1 ⁇ m
  • the electrode spacing is 6.5 ⁇ m
  • the phase shifter modulation efficiency is approximately 2 V ⁇ cm.
  • the present invention can effectively improve its stability and reliability, improve multiple properties of the fiber optic gyroscope, and achieve smaller size, lower power consumption, lower cost, simpler structural design and more of the fiber optic gyroscope. Craftsmanship.

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Abstract

一种光学陀螺双层SiN基集成驱动芯片，芯片的第一种实现结构包括第一光纤-SiN波导耦合器(1-1)、第二光纤-SiN波导耦合器(1-2)、第一3dB分束器(9)、起偏器(10)、第二3dB分束器(11)、第一层间垂直耦合器(5-1)、第二层间垂直耦合器(5-2)、第一相移器(6-1)、第二相移器(6-2)、第三层间垂直耦合器(5-3)、第四层间垂直耦合器(5-4)、第三光纤-SiN波导耦合器(7-1)、第四光纤-SiN波导耦合器(7-2)。由于结合了SiN光子平台良好的可扩展性和电光材料的出色的电光调制性能，上层的SiN波导（1-1、1-2、7-1、7-2）可以在整个芯片上实现低损耗的光传输、分束和起偏，而下层的电光相移器（6-1、6-2）可与全套SiN光子组件进行集成，使得所提出的芯片架构非常适合光纤陀螺等应用。

Description

光学陀螺双层SiN基集成驱动芯片
本申请要求于2022年06月30日提交中国专利局、申请号为202210754271.0、发明名称为“光学陀螺双层SiN基集成驱动芯片”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本发明涉及集成光学和惯性传感技术领域，尤其涉及光学陀螺双层SiN基集成驱动芯片。
背景技术
作为一种角速度传感器，光纤陀螺相比传统机械陀螺在测量精度、灵敏度和可靠性等方面具有显著的优势，被广泛应用于定位、姿态控制和绝对方向测量等方面。按照测量精度的划分，高精度的光纤陀螺主要应用在空间技术、军事应用和科学研究领域，而低成本的中低精度光纤陀螺在汽车导航、定位和姿态控制、机器人等许多民用领域有着广阔的应用场景。
光纤陀螺一般基于分离的光纤器件实现光信号的产生、调制以及探测，不同的光纤器件通过尾纤熔接形成Sagnac干涉光学回路，从而不可避免地产生如寄生反射、连接点处增加的插入损耗以及对环境敏感的偏振失配等一系列问题，上述情况均会不同程度的降低系统性能。另外，采用一系列分离光纤器件还会增大系统尺寸以及重量。近年来随着集成光子学的发展，研究者们提出了集成光学陀螺以解决上述问题。通过将除传感线圈外光学陀螺需要的所有有源和无源光学器件集成在同一个芯片上，构成集成光学驱动芯片。该芯片可以同传感线圈(如保偏光纤或超低损耗的氮化硅波导等)连接在一起形成干涉光学陀螺，从而大大减少了光学陀螺的尺寸、重量、功耗以及成本，可以为光学陀螺的快速普及起到重要的推动作用。
另一方面，对于干涉型光学陀螺，稳定的相位调制是实现系统中Sagnac相位差信号高灵敏度、高准确度提取的重要保证，从而要求相移器具备较高的调制响应度、调制线性度以及大调制带宽等性能特性。目前在光纤陀螺系统中得到广泛应用的集成相移器主要基于体铌酸锂波导中的电光效应实现，但是基于质子扩散工艺的传统LiNbO 3波导存在一些不 足：
(1)波导和包层之间较低的折射率差导致较弱的光场限制，从而需要金属电极与波导保持较大的间隔，进而降低了电光调制效率。
(2)对质子交换的时间、温度、交换介质的特性及退火的温度和时间有严格要求，制备工艺复杂且成本较高。
氮化硅(SiN)作为一种CMOS兼容的材料，能够用标准的CMOS工艺加工，而且具有二氧化硅包层的SiN波导的较低折射率对比度降低了由于侧壁粗糙度、色散和对波导尺寸变化的敏感性而导致的波导损耗，SiN的光学透明窗口可覆盖近红外和可见光波长范围，使其适用于非光通信领域。因此，近年来，氮化硅平台已经成为集成光学的常见工艺平台。但是，SiN没有二阶非线性效应(从而缺少线性电光效应)，三阶非线性效应较弱，且不支持电子掺杂，故无法实现高效、快速的电光调制。
上述问题可以通过在SiN平台上的低折射率包层，例如二氧化硅(SiO 2)上异质集成非中心对称材料薄膜来解决，以实现高二阶非线性和较高的模场限制能力，同时仍具有与CMOS加工工艺的兼容性。典型异质集成材料包括：铁电体，例如铌酸锂薄膜(LiNbO 3)；化合物半导体，例如铝-镓-砷(AlGaAs)和铝-镓-氮化物(AlGaN)系列；石墨烯和聚合物等。因此，利用薄膜沉积、外延生长和晶圆键合技术，在SiN材料中无法实现或性能不足的主动器件可以通过特定的异质集成材料实现并集成在单个SiN芯片上。
近来，LiNbO 3薄膜与SiN/Si光子集成平台的异质集成受到了广泛的关注和研究。异质集成的SiN/Si-LiNbO 3薄膜材料系统结合了SiN/Si光子平台良好的可扩展性和LiNbO 3出色的电光调制性能。所实现的电光调制器件(如电光相位和强度调制器)显示出了大调制带宽、高调制效率、低片上插入损耗和高线性度的优势，其性能水平能够媲美其他材料集成平台的最优水平，而且还可以克服一些传统的局限。底层的SiN/Si波导不仅可以在整个芯片上实现低损耗的光路由，而且还允许将该电光调制器与全套SiN/Si光子组件进行集成，这使得所提出的SiN/Si-LiNbO 3平台非常适合新兴应用。因此，基于异质集成薄膜电光材料的集成光子学正在成为当前学界和工业界的热门领域。
发明内容
本发明实施例所要解决的技术问题在于，提供一种光学陀螺双层SiN基集成驱动芯片，以提高其稳定性和准确度，同时适用于830nm、850nm、1310nm以及1550nm等光纤陀螺可用的波段。
为了解决上述技术问题，本发明实施例提出了一种光学陀螺双层SiN基集成驱动芯片，所述芯片从上到下包括SiO 2上包层、SiN上层、SiO 2中间层、SiN下层、电光材料薄膜层、SiO 2下包层、Si衬底层；所述芯片采用第一种实现结构或第二种实现结构，其中，
所述芯片的第一种实现结构包括在SiN上层中实现的第一光纤-SiN波导耦合器、第二光纤-SiN波导耦合器、第一3dB分束器、起偏器、第二3dB分束器、第一层间垂直耦合器上波导taper、第二层间垂直耦合器上波导taper、第三层间垂直耦合器上波导taper、第四层间垂直耦合器上波导taper、第三光纤-SiN波导耦合器、第四光纤-SiN波导耦合器；在SiN下层中实现的第一层间垂直耦合器下波导taper、第二层间垂直耦合器下波导taper、第一相移器、第二相移器、第三层间垂直耦合器下波导taper、第四层间垂直耦合器下波导taper；
外部光源通过光纤与第一光纤-SiN波导耦合器一端相连；外部光电探测器通过光纤与第二光纤-SiN波导耦合器一端相连；第一光纤-SiN波导耦合器的另一端与第二光纤-SiN波导耦合器的另一端分别与第一3dB分束器的两个分支相连；第一3dB分束器的基波导与起偏器的一端相连；起偏器的另一端与第二3dB分束器的基波导相连；第二3dB分束器的两个分支分别与第一、第二层间垂直耦合器上波导taper的一端相连；间隔一定厚度的SiO 2中间层，第一、第二层间垂直耦合器上波导taper的正下方分别为第一、第二层间垂直耦合器下波导taper；第一、第二层间垂直耦合器下波导taper的一端分别与第一、第二相移器的一端相连；第一、第二相移器的另一端分别与第三、第四层间垂直耦合器下波导taper的一端相连；间隔一定厚度的SiO 2中间层，第三、第四层间垂直耦合器下波导taper的正上方分别为第三、第四层间垂直耦合器上波导taper；第三、第四层间垂直耦合器上波导taper的一端分别与第三、第四光纤-SiN波导耦合器的一端相连；第三、第四光纤-SiN波导耦合器的另一端分别与外 部光纤环的两端相连；
芯片的第二种实现结构包括在SiN上层中实现的第一光纤-SiN波导耦合器、第二光纤-SiN波导耦合器、第一3dB分束器、起偏器、第二3dB分束器、第一层间垂直耦合器上波导taper、第二层间垂直耦合器上波导taper；在SiN下层中实现的第一层间垂直耦合器下波导taper、第二层间垂直耦合器下波导taper、第一相移器、第二相移器、第一光纤-SiN/电光材料混合波导耦合器、第二光纤-SiN/电光材料混合波导耦合器；
外部光源通过光纤与第一光纤-SiN波导耦合器一端相连；外部光电探测器通过光纤与第二光纤-SiN波导耦合器一端相连；第一光纤-SiN波导耦合器的另一端与第二光纤-SiN波导耦合器的另一端分别与第一3dB分束器的两个分支相连；第一3dB分束器的基波导与起偏器的一端相连；起偏器的另一端与第二3dB分束器的基波导相连；第二3dB分束器的两个分支分别与第一、第二层间垂直耦合器上波导taper的一端相连；间隔一定厚度的SiO 2中间层，第一、第二层间垂直耦合器上波导taper的正下方分别为第一、第二层间垂直耦合器下波导taper；第一、第二层间垂直耦合器下波导taper的一端分别与第一、第二相移器的一端相连；第一、第二相移器的另一端分别与第一、第二光纤-SiN/电光材料混合波导耦合器的一端相连；第一、第二光纤-SiN/电光材料混合波导耦合器的另一端分别与外部光纤环的两端相连。
进一步地，所述芯片的工作波段为830nm、850nm、1310nm以及1550nm中的一种或多种。
进一步地，所述SiO 2上包层上还设有用来吸收芯片结构中杂散光的多晶硅层。
进一步地，所述SiO 2中间层位于SiN上层和SiN下层之间。
进一步地，所述光纤-SiN波导耦合器均采用inversed taper结构实现在芯片端面处波导与保偏光纤之间的模场直径匹配。
进一步地，所述光纤-SiN/电光材料混合波导耦合器均采用inversed taper结构实现在芯片端面处混合波导与保偏光纤之间的模场直径匹配。进一步地，所述3dB分束器均采用Y型分束器或1×2多模干涉仪分束器实现。
进一步地，所述起偏器采用固定弯曲半径或曲率连续的弯曲波导结构实现。
进一步地，所述层间垂直耦合器均采用上下反向taper结构实现光在上层SiN波导和下层SiN-电光材料混合波导之间的耦合。
进一步地，所述第一相移器和第二相移器利用异质集成薄膜电光材料的线性电光效应实现相位调制，采用底部键合电光材料薄膜层的混合SiN波导结构来实现。
本发明的有益效果为：
1、基于异质集成薄膜电光材料的电光相移器的光学陀螺双层SiN基集成驱动芯片，结合了SiN光子平台良好的可扩展性和电光材料的出色的电光调制性能：上层的SiN波导可以在整个芯片上实现低损耗的光传输、分束和起偏，而下层的电光相移器可与全套SiN光子组件进行集成，使得所提出的芯片架构非常适合光纤陀螺等应用。
2、基于异质集成薄膜电光材料线性电光效应的相移器设计，可以确保在近红外波段实现高线性度、高带宽(>1GHz)、低插损(<1dB)的相位调制。
3、SiN材料较小的热光系数确保环境温度变化对器件的光学传输特性影响较小，进而抑制温度漂移效应，提高陀螺的稳定性；另外，SiN材料在近红外波长区域具有高透射性，故基于SiN光学集成芯片的光纤陀螺可以工作在短波长区域，从而具有更大的标度因子。
4、通过采用集成光学器件，避免了寄生反射、连接点插入损耗以及偏振失配等问题，进一步提高系统可靠性、减小系统体积以及降低系统成本。
说明书附图
图1是本发明实施例的光学陀螺双层SiN基集成驱动芯片的系统组成示意图。
图2是本发明实施例的光学陀螺双层SiN基集成驱动芯片的第一种实现结构的透视示意图。
图3是本发明实施例的光学陀螺双层SiN基集成驱动芯片的第一种实现结构的光路图。
图4是本发明实施例的光学陀螺双层SiN基集成驱动芯片的第二种实现结构的透视示意图。
图5是本发明实施例的光学陀螺双层SiN基集成驱动芯片的第二种实现结构的光路图。
图6是本发明实施例的层间垂直耦合器结构示意图。
图7是本发明实施例的起偏器的结构示意图。
图8是本发明实施例的相移器结构示意图。
附图标号说明：
多晶硅层1、SiO 2上包层2、SiN上层3、SiO 2中间层4、SiN下层5、电光材料薄膜层6、SiO 2下包层7、Si衬底层8、第一光纤-SiN波导耦合器1-1、第二光纤-SiN波导耦合器1-2、第一3dB分束器9、起偏器10、第二3dB分束器11、第一层间垂直耦合器5-1、第二层间垂直耦合器5-2、第一相移器6-1、第二相移器6-2、第三层间垂直耦合器5-3、第四层间垂直耦合器5-4、第三光纤-SiN波导耦合器7-1、第四光纤-SiN波导耦合器7-2、标号12的箭头方向为外部光源输入的方向，标号13的箭头方向为输出到外部探测器的光的方向。
具体实施方式
本发明实施例的光学陀螺双层SiN基集成驱动芯片的层级组成从上到下依次为SiO2上包层2、SiN上层3、SiO 2中间层4、SiN下层5、电光材料薄膜层6、SiO 2下包层7、Si衬底层8。此外，SiO 2上包层2上还设有用来吸收芯片结构中杂散光的多晶硅层1。本发明实施例的光学陀螺双层SiN基集成驱动芯片的系统组成如图1所示。
请参照图2和图3，本发明实施例的光学陀螺双层SiN基集成驱动芯片的第一种实现结构包括：第一光纤-SiN波导耦合器1-1，第二光纤-SiN波导耦合器1-2，第一3dB分束器9，起偏器10，第二3dB分束器11，第一层间垂直耦合器5-1，第二层间垂直耦合器5-2，第一相移器6-1，第二相移器6-2，第三层间垂直耦合器5-3，第四层间垂直耦合器5-4，第三光纤-SiN波导耦合器7-1，第四光纤-SiN波导耦合器7-2。
外部光源通过光纤与第一光纤-SiN波导耦合器1-1一端相连；外部光电探测器通过光纤与第二光纤-SiN波导耦合器1-2一端相连；第一光纤 -SiN波导耦合器1-1的另一端与第二光纤-SiN波导耦合器1-2的另一端分别与第一3dB分束器9的两个分支相连；第一3dB分束器9的基波导与起偏器10的一端相连；起偏器10的另一端与第二3dB分束器11的基波导相连；第二3dB分束器11的两个分支分别与第一层间垂直耦合器5-1上波导taper、第二层间垂直耦合器5-2上波导taper的一端相连；间隔一定厚度的SiO2中间层4，第一层间垂直耦合器5-1上波导taper、第二层间垂直耦合器5-2上波导taper的正下方分别为第一层间垂直耦合器5-1下波导taper、第二层间垂直耦合器5-2下波导taper；第一层间垂直耦合器5-1下波导taper、第二层间垂直耦合器5-2下波导taper的一端分别与第一相移器6-1、第二相移器6-2的一端相连；第一相移器6-1、第二相移器6-2的另一端分别与第三层间垂直耦合器5-3下波导taper、第四层间垂直耦合器5-4下波导taper的一端相连；间隔一定厚度的SiO2中间层4，第三层间垂直耦合器5-3下波导taper、第四层间垂直耦合器5-4下波导taper的正上方分别为第三层间垂直耦合器5-3上波导taper、第四层间垂直耦合器5-4上波导taper；第三层间垂直耦合器5-3上波导taper、第四层间垂直耦合器5-4上波导taper的一端分别与第三光纤-SiN波导耦合器7-1、第四光纤-SiN波导耦合器7-2的一端相连；第三光纤-SiN波导耦合器7-1、第四光纤-SiN波导耦合器7-2的另一端分别与外部光纤环的两端相连。
以图3所示结构为例，外部光源输出的光经光纤沿箭头12标识的方向耦合到芯片上的第一光纤-SiN波导耦合器1-1，第一光纤-SiN波导耦合器1-1输出的光包含两种不同的偏振模式(准TE 0和TM 0)；两种不同的偏振模式通过第一3dB分束器9后，进入起偏器10，由于起偏器10的偏振选择，将准TM 0模式泄露到了SiO 2包层中，而在SiN波导中只保留了准TE 0模式；该TE 0模式进入第二3dB分束器11并分成两束，一束经第一层间垂直耦合器5-1上波导taper通过层间垂直耦合进入第一层间垂直耦合器5-1下波导taper；然后经第一相移器6-1相位调制后，进入第三层间垂直耦合器5-3下波导taper，经层间垂直耦合进入第三层间垂直耦合器5-3上波导taper，然后通过第三光纤-SiN波导耦合器7-1耦合进入光纤环；另一束经第二层间垂直耦合器5-2上波导taper通过层间垂直耦合 进入第二层间垂直耦合器5-2下波导taper；然后经第二相移器6-2相位调制后，进入第四层间垂直耦合器5-4下波导taper，经层间垂直耦合进入第四层间垂直耦合器5-4上波导taper，然后通过第四光纤-SiN波导耦合器7-2耦合进入光纤环；这两束光在光纤环中分别沿顺时针和逆时针方向相向传播，且两束光满足相干条件。当光纤环绕其中心轴发生转动后，产生了Sagnac效应，从而沿上述路径回到第二3dB分束器11处的干涉光强发生变化；该干涉光信号经第二3dB分束器11、起偏器10、第一3dB分束器9、第二光纤-SiN波导耦合器1-2后，沿箭头13标识的方向耦合输出到外部光电探测器，从而检测出变化的光强，经处理后即得转动角速度信息。
请参照图4和图5，本发明实施例的光学陀螺双层SiN基集成驱动芯片的第二种实现结构包括：第一光纤-SiN波导耦合器1-1，第二光纤-SiN波导耦合器1-2，第一3dB分束器9，起偏器10，第二3dB分束器11，第一层间垂直耦合器5-1，第二层间垂直耦合器5-2，第一相移器6-1，第二相移器6-2，第一光纤-SiN/电光材料混合波导耦合器7-1，第二光纤-SiN/电光材料混合波导耦合器7-2。
外部光源通过光纤与第一光纤-SiN波导耦合器1-1一端相连；外部光电探测器通过光纤与第二光纤-SiN波导耦合器1-2一端相连；第一光纤-SiN波导耦合器1-1的另一端与第二光纤-SiN波导耦合器1-2的另一端分别与第一3dB分束器9的两个分支相连；第一3dB分束器9的基波导与起偏器10的一端相连；起偏器10的另一端与第二3dB分束器11的基波导相连；第二3dB分束器11的两个分支分别与第一层间垂直耦合器5-1上波导taper、第二层间垂直耦合器5-2上波导taper的一端相连；间隔一定厚度的SiO2中间层4，第一层间垂直耦合器5-1上波导taper、第二层间垂直耦合器5-2上波导taper的正下方分别为第一层间垂直耦合器5-1下波导taper、第二层间垂直耦合器5-2下波导taper；第一层间垂直耦合器5-1下波导taper、第二层间垂直耦合器5-2下波导taper的一端分别与第一相移器6-1、第二相移器6-2的一端相连；第一相移器6-1、第二相移器6-2的另一端分别与第一光纤-SiN/电光材料混合波导耦合器7-1、第二光纤-SiN/电光材料混合波导耦合器7-2的一端相连；第一光纤-SiN/电光 材料混合波导耦合器7-1、第二光纤-SiN/电光材料混合波导耦合器7-2的另一端分别与外部光纤环的两端相连。
以图5所示结构为例，外部光源输出的光经光纤沿箭头12标识的方向耦合到芯片上的第一光纤-SiN波导耦合器1-1，第一光纤-SiN波导耦合器1-1输出的光包含两种不同的偏振模式(准TE 0和TM 0)；两种不同的偏振模式通过第一3dB分束器9后，进入起偏器10，由于起偏器10的偏振选择，将准TM 0模式泄露到了SiO 2包层中，而在SiN波导中只保留了准TE 0模式；该TE 0模式进入第二3dB分束器11并分成两束，一束经第一层间垂直耦合器5-1上波导taper通过层间垂直耦合进入第一层间垂直耦合器5-1下波导taper；然后经第一相移器6-1相位调制后，通过第一光纤-SiN/电光材料混合波导耦合器7-1耦合进入光纤环；另一束经第二层间垂直耦合器5-2上波导taper通过层间垂直耦合进入第二层间垂直耦合器5-2下波导taper；然后经第二相移器6-2相位调制后，通过第二光纤-SiN/电光材料混合波导耦合器7-2耦合进入光纤环；这两束光在光纤环中分别沿顺时针和逆时针方向相向传播，且两束光满足相干条件。当光纤环绕其中心轴发生转动后，产生了Sagnac效应，从而沿上述路径回到第二3dB分束器11处的干涉光强发生变化；该干涉光信号经第二3dB分束器11、起偏器10、第一3dB分束器9、第二光纤-SiN波导耦合器1-2后，沿箭头13标识的方向耦合输出到外部光电探测器，从而检测出变化的光强，经处理后即得转动角速度信息。本发明的起偏器采用基于连续曲率弯曲波导的起偏器。
作为一种实施方式，所述光纤-SiN波导耦合器均采用inversed taper结构实现端面处SiN波导与保偏光纤之间的模场匹配。在该实施例中，通过优化inversed taper结构中波导最小宽度和taper长度，在近红外波段可实现与超细径保偏光纤(包层直径为40μm，纤芯直径为3μm)的模场匹配，耦合效率大于90％。
作为一种实施方式，所述光纤-SiN/电光材料混合波导耦合器采用inversedtaper结构实现端面处SiN-电光材料混合波导与保偏光纤之间的模场匹配。在该实施例中，通过优化inversed taper结构的SiN最小宽度和taper长度，在近红外波段可实现与超细径保偏光纤(包层直径为40μm， 纤芯直径为3μm)的模场匹配，耦合效率大于90％。
作为一种实施方式，所述层间垂直耦合器采用上下反向taper结构实现光在上层SiN波导和下层SiN-电光材料混合波导之间的耦合，其结构如图6所示，设计参数包括上、下层taper的最小宽度和长度以及中间SiO 2层的厚度。在该实施例中，上层SiN波导尺寸为1200×45nm，下层混合SiN-电光材料波导尺寸为1200×100nm，优化后的上层taper的最小宽度和长度分别为250nm、2.5um，下层taper的最小宽度和长度分别为150nm、2.5um，中间SiO 2层的厚度为1um，对应的层间耦合效率为95％。
作为一种实施方式，所述第一3dB分束器9和第二3dB分束器11采用Y型分束器实现。在该实施例中，通过对Y型结构优化设计，在近红外波段准TE 0模式在每个端口的透过率>49％。
作为一种实施方式，所述起偏器10由具有曲率连续分布的弯曲波导组成，其结构如图7所示。在目标工作波长范围内，通过合理设计波导横向尺寸、波导弯曲曲率分布以及弯曲波导长度，实现：(1)波导内仅支持准TE 0/TM 0两个模式，且二者之间有足够大的有效折射率差，故TM 0的弯曲辐射损耗远大于TE 0；(2)准TE 0/TM 0两个模式之间的偏振消光比大于50dB，且准TE 0模式的传播损耗小于0.5dB；(3)从输入端到输出端曲率连续分布，避免TE 0模式由于曲率不连续引起的散射损耗。在该实施例中，SiN波导尺寸为1200×45nm，最小弯曲半径为500μm，弯曲波导总的长度为5mm。
作为一种实施方式，所述相移器采用底部键合电光材料层的混合SiN波导结构来实现；薄膜电光材料选择LiNO 3晶体，其电光系数r 33为30pm/V，晶体切割采用x-cut or y-cut方案。相移器结构设计如图8所示，在SiN波导底部键合薄膜电光材料，采用了push-pull结构。相移器包括SiO 2包层、金属电极和SiN波导、薄膜电光材料、SiO 2包层、Si衬底。通过合理优化薄膜电光材料的厚度、两电极间隔以及SiN波导宽度，最大化相移器的调制效率以及最小化波导传输损耗。在该实施例中，混合SiN-LiNO 3波导尺寸为1200×100nm，LiNO 3薄膜的厚度为1μm，电极间隔6.5um，相移器调制效率约为2V·cm。
本发明在保证光纤陀螺精度的同时，可有效提高其稳定性、可靠性， 提高光纤陀螺的多项性能，实现光纤陀螺的更小型化、更低功耗、更低成本、更简单结构设计及工艺。

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  1. 光学陀螺双层SiN基集成驱动芯片，其特征在于，所述芯片从上到下包括SiO 2上包层、SiN上层、SiO 2中间层、SiN下层、电光材料薄膜层、SiO 2下包层、Si衬底层；所述芯片采用第一种实现结构或第二种实现结构，其中，
    所述芯片的第一种实现结构包括在SiN上层中实现的第一光纤-SiN波导耦合器、第二光纤-SiN波导耦合器、第一3dB分束器、起偏器、第二3dB分束器、第一层间垂直耦合器上波导taper、第二层间垂直耦合器上波导taper、第三层间垂直耦合器上波导taper、第四层间垂直耦合器上波导taper、第三光纤-SiN波导耦合器、第四光纤-SiN波导耦合器；在SiN下层中实现的第一层间垂直耦合器下波导taper、第二层间垂直耦合器下波导taper、第一相移器、第二相移器、第三层间垂直耦合器下波导taper、第四层间垂直耦合器下波导taper；
    外部光源通过光纤与第一光纤-SiN波导耦合器一端相连；外部光电探测器通过光纤与第二光纤-SiN波导耦合器一端相连；第一光纤-SiN波导耦合器的另一端与第二光纤-SiN波导耦合器的另一端分别与第一3dB分束器的两个分支相连；第一3dB分束器的基波导与起偏器的一端相连；起偏器的另一端与第二3dB分束器的基波导相连；第二3dB分束器的两个分支分别与第一、第二层间垂直耦合器上波导taper的一端相连；间隔一定厚度的SiO 2中间层，第一、第二层间垂直耦合器上波导taper的正下方分别为第一、第二层间垂直耦合器下波导taper；第一、第二层间垂直耦合器下波导taper的一端分别与第一、第二相移器的一端相连；第一、第二相移器的另一端分别与第三、第四层间垂直耦合器下波导taper的一端相连；间隔一定厚度的SiO 2中间层，第三、第四层间垂直耦合器下波导taper的正上方分别为第三、第四层间垂直耦合器上波导taper；第三、第四层间垂直耦合器上波导taper的一端分别与第三、第四光纤-SiN波导耦合器的一端相连；第三、第四光纤-SiN波导耦合器的另一端分别与外部光纤环的两端相连；
    芯片的第二种实现结构包括在SiN上层中实现的第一光纤-SiN波导耦合器、第二光纤-SiN波导耦合器、第一3dB分束器、起偏器、第二3dB分束器、第一层间垂直耦合器上波导taper、第二层间垂直耦合器上波导 taper；在SiN下层中实现的第一层间垂直耦合器下波导taper、第二层间垂直耦合器下波导taper、第一相移器、第二相移器、第一光纤-SiN/电光材料混合波导耦合器、第二光纤-SiN/电光材料混合波导耦合器；
    外部光源通过光纤与第一光纤-SiN波导耦合器一端相连；外部光电探测器通过光纤与第二光纤-SiN波导耦合器一端相连；第一光纤-SiN波导耦合器的另一端与第二光纤-SiN波导耦合器的另一端分别与第一3dB分束器的两个分支相连；第一3dB分束器的基波导与起偏器的一端相连；起偏器的另一端与第二3dB分束器的基波导相连；第二3dB分束器的两个分支分别与第一、第二层间垂直耦合器上波导taper的一端相连；间隔一定厚度的SiO 2中间层，第一、第二层间垂直耦合器上波导taper的正下方分别为第一、第二层间垂直耦合器下波导taper；第一、第二层间垂直耦合器下波导taper的一端分别与第一、第二相移器的一端相连；第一、第二相移器的另一端分别与第一、第二光纤-SiN/电光材料混合波导耦合器的一端相连；第一、第二光纤-SiN/电光材料混合波导耦合器的另一端分别与外部光纤环的两端相连。
  2. 如权利要求1所述的光学陀螺双层SiN基集成驱动芯片，其特征在于，所述芯片的工作波段为830nm、850nm、1310nm以及1550nm中的一种或多种。
  3. 如权利要求1所述的光学陀螺双层SiN基集成驱动芯片，其特征在于，所述SiO 2上包层上还设有用来吸收芯片结构中杂散光的多晶硅层。
  4. 如权利要求1所述的光学陀螺双层SiN基集成驱动芯片，其特征在于，所述SiO 2中间层位于SiN上层和SiN下层之间。
  5. 如权利要求1所述的光学陀螺双层SiN基集成驱动芯片，其特征在于，所述光纤-SiN波导耦合器均采用inversed taper结构实现在芯片端面处波导与保偏光纤之间的模场直径匹配。
  6. 如权利要求1所述的光学陀螺双层SiN基集成驱动芯片，其特征在于，所述光纤-SiN/电光材料混合波导耦合器均采用inversed taper结构实现在芯片端面处混合波导与保偏光纤之间的模场直径匹配。
  7. 如权利要求1所述的光学陀螺双层SiN基集成驱动芯片，其特征在于，所述3dB分束器均采用Y型分束器或1×2多模干涉仪分束器实现。
  8. 如权利要求1所述的光学陀螺双层SiN基集成驱动芯片，其特征在于，所述起偏器采用固定弯曲半径或曲率连续的弯曲波导结构实现。
  9. 如权利要求1所述的光学陀螺双层SiN基集成驱动芯片，其特征在于，所述层间垂直耦合器均采用上下反向taper结构实现光在上层SiN波导和下层SiN-电光材料混合波导之间的耦合。
  10. 如权利要求1所述的光学陀螺双层SiN基集成驱动芯片，其特征在于，所述第一相移器和第二相移器利用异质集成薄膜电光材料的线性电光效应实现相位调制，采用底部键合电光材料薄膜层的混合SiN波导结构来实现。
PCT/CN2022/126598 2022-06-30 2022-10-21 光学陀螺双层SiN基集成驱动芯片 WO2024000936A1 (zh)

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