An on-chip integrated chip of a laser radar based on acousto-optic modulation, an on-chip acousto-optic scanning method and a laser radar system

Abstract

The application relates to a laser radar on-chip integrated chip based on acousto-optic modulation, an on-chip acousto-optic scanning method and a laser radar system. A plurality of groups of interdigital transducers are arranged on a lithium niobate film, wherein two groups of chirped IDTs work at a low-frequency band and a high-frequency band respectively, a low-frequency band acoustic wave corresponds to generating a larger Bragg deflection angle; a high-frequency band acoustic wave corresponds to generating a smaller Bragg deflection angle. Two groups of IDTs work cooperatively to realize two-dimensional vector scanning of a double-frequency wide band in a chip plane; a pair of focusing type IDTs arranged can form a focused acoustic field in an action area, so that a light beam deflected in two directions is controllably deflected in a Z direction, thereby endowing the chip with three-dimensional scanning capability. The application has high diffraction efficiency and low power consumption; the unification of wide-range search and high-precision scanning is realized; Z-axis deflection is realized through integration of a special focusing type interdigital transducer, three-dimensional scanning function is realized on the single-chip integrated acousto-optic chip, and the structure is extremely compact.

Description

Technical Field

[0001] This application relates to the fields of integrated photonics and optoelectronics, and more specifically, to an on-chip integrated chip for lidar based on acousto-optic modulation, an on-chip acousto-optic scanning method, and a lidar system. Background Technology

[0002] The beam scanning scheme of lidar mainly includes MEMS micromirrors, optical phased arrays (OPA), and acousto-optic deflectors (AOD). MEMS relies on mechanical oscillation, which has limitations due to inertia and resonance, and its shock resistance and long-term reliability are challenged. OPA requires large-scale phase modulators, which are prone to sidelobes, thermal crosstalk, and high power consumption, and the field of view is limited. Free-space AOD is bulky, which is not conducive to chip-level integration. Existing on-chip AODs are mostly based on silicon / silicon nitride platforms, which have low acousto-optic coefficients and poor overlap between acoustic energy and optical modes, resulting in small usable acoustic vectors, limited deflection angles, low extinction ratios, and high RF power consumption. Two-dimensional scanning usually requires multi-level device stacking, which easily introduces acoustic reflections and channel crosstalk. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of existing on-chip beam scanning technologies, such as small deflection angle, low diffraction efficiency, high power consumption, poor extinction ratio, and difficulty in integrating two-dimensional / three-dimensional scanning. On the one hand, it provides an on-chip integrated chip for lidar based on acousto-optic modulation and an on-chip acousto-optic scanning method, which can achieve on-chip three-dimensional scanning functions with wide field of view, high speed, high resolution, and compact structure. On the other hand, it also provides a lidar system that can realize three-dimensional environmental imaging.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0005] An on-chip integrated circuit for lidar based on acousto-optic modulation is provided, comprising:

[0006] Insulating substrate;

[0007] A lithium niobate thin film layer disposed on an insulating substrate;

[0008] A chalcogenide glass waveguide layer is covered on the lithium niobate thin film layer, and the chalcogenide glass waveguide layer is etched to form an optical waveguide and an action region for acousto-optic interaction;

[0009] The system includes multiple sets of interdigital transducers arranged above, below, or adjacent to the active region to excite surface acoustic waves or Love waves in the composite structure composed of the lithium niobate thin film layer and the chalcogenide glass waveguide layer. These include at least two sets of apodization-weighted chirped interdigital transducers, whose acoustic wave propagation directions are non-collinear. They operate in preset high-frequency and low-frequency bands, respectively. By changing the driving frequency, the waveguide light undergoes Bragg diffraction and two-dimensional deflection in the active region, thereby achieving dual-frequency broadband two-dimensional scanning within the chip plane. It also includes at least one pair of focusing interdigital transducers, with the focusing direction pointing towards the light output path of the active region. These transducers form a focused acoustic field within the active region, causing the two-dimensionally deflected light beam to undergo controllable deflection in the Z direction perpendicular to the chip plane, thereby achieving three-dimensional scanning of the chip.

[0010] This invention provides an on-chip integrated circuit (ICC) for lidar based on acousto-optic modulation (AIDM). Multiple interdigital transducers (IDTs) are arranged on a lithium niobate thin film. Two sets of apodization-weighted chirped IDTs operate in the low-frequency and high-frequency bands, respectively. Through frequency sweeping, the low-frequency acoustic waves generate a larger Bragg deflection angle, achieving a wide-range scan; the high-frequency acoustic waves generate a smaller Bragg deflection angle, achieving high-precision scanning. The two IDTs work together to achieve dual-frequency broadband two-dimensional vector scanning within the chip plane. A pair of focusing interdigital transducers forms a focused sound field within the operating area, causing the beam, after two-dimensional deflection, to undergo controllable deflection in the Z-direction perpendicular to the chip plane, thus endowing the chip with three-dimensional scanning capabilities. This invention employs a heterogeneous integrated structure of lithium niobate thin film and chalcogenide glass, resulting in high diffraction efficiency and low power consumption. Through a dual-frequency broadband collaborative scanning mechanism of "large deflection in the low-frequency band" and "small deflection in the high-frequency band," it achieves a unified approach to wide-range searching and high-precision scanning. By integrating a dedicated focusing interdigital transducer to achieve Z-axis deflection, it realizes three-dimensional scanning functionality on a single integrated acousto-optic chip, resulting in an extremely compact structure that avoids the challenges of size, packaging, and alignment caused by multi-chip stacking or external scanning modules.

[0011] Furthermore, the electrode thickness of the interdigital transducer is preferably 80 nm to 200 nm, which can efficiently excite surface acoustic waves in the frequency range of 80 MHz to 2 GHz.

[0012] Furthermore, the chirped interdigital transducer simultaneously features electrode periodic chirping and electrode envelope weighting to broaden the acoustic bandwidth and suppress sidelobes.

[0013] Furthermore, the electrode period of the chirped interdigital transducer is preferably 0.4 μm to 3 μm, corresponding to a center frequency of 0.8 GHz to 5 GHz.

[0014] Furthermore, the focusing interdigital transducer is an arc-shaped, elliptical, or phase-encoded structure, used to form a locally enhanced acoustic field in the active area, so that the emitted light is controllably deflected in the Z direction perpendicular to the chip plane.

[0015] Furthermore, multiple sets of interdigital transducers are arranged in parallel according to frequency band segments, with each segment partially overlapping the others, in order to expand the total scanning bandwidth and field of view while maintaining high diffraction efficiency.

[0016] Furthermore, the thickness of the chalcogenide glass waveguide layer and the thickness of the lithium niobate thin film layer satisfy the dispersion condition of the Love wave waveguide mode, so that the acoustic energy is coupled to the chalcogenide glass waveguide layer and the optical mode achieves maximum overlap.

[0017] Furthermore, the optical coupling between the chalcogenide glass waveguide layer and the outside world adopts an outgoing grating coupler. The period and tilt angle of the outgoing grating are designed in coordination with the acoustic wave vector scanning range to map the deflection in the waveguide into a large field of view scan in free space.

[0018] Furthermore, the material of the chalcogenide glass waveguide layer is one or more of As2S3, As2Se3, Ge–As–Se or Ge–Sb–Se; the lithium niobate thin film layer is X-cut, Y-cut or 128°YX-cut oriented.

[0019] Furthermore, the width of the chalcogenide optical waveguide is preferably 300 nm to 30 µm, and the height is preferably 200 nm to 500 nm, in order to support single-mode or few-mode optical wave transmission in communication bands (e.g., 1550 nm C-band).

[0020] Furthermore, acoustic absorption structures and / or bent acoustic waveguide structures are provided on both sides of the active area to reduce acoustic reflection and channel crosstalk.

[0021] Furthermore, the acoustic absorption structure includes one or more of a polymer absorption layer, a micro / nano groove-type energy dissipation structure, or a porous dielectric layer, and is disposed on the outer periphery of the active area to suppress boundary reflections and crosstalk.

[0022] Furthermore, at least two acousto-optic units are connected in series in the active region along the light propagation direction and driven in a push-pull, in-phase, or out-of-phase manner to improve the extinction ratio or diffraction efficiency.

[0023] Furthermore, it also includes an impedance matching network, a power combining and distribution network, and a temperature compensation heater electrically connected to the interdigital transducer to stabilize the Bragg matching conditions.

[0024] Furthermore, several of the above-mentioned chips can be cascaded using waveguide couplers to form a scanning function with a wider range and greater angle. Waveguide couplers include multimode interference waveguides, beam splitters, photonic leads, etc.

[0025] This invention also provides an on-chip acousto-optic scanning method, employing the aforementioned acousto-optic modulation-based lidar on-chip integrated chip, comprising:

[0026] One set of the chirped interdigital transducers is driven in the low-frequency band; the other set of the chirped interdigital transducers is driven in the high-frequency band; the acoustic wave vector magnitudes of the two sets of chirped interdigital transducers are changed by frequency sweep, and time division multiplexing or frequency division multiplexing is performed between the two sets of chirped interdigital transducers; by adjusting the relative amplitude and phase of the two sets of chirped interdigital transducers, an equivalent acoustic grating of the target vector is synthesized, thereby realizing two-dimensional deflection in the plane within the waveguide;

[0027] The focused interdigital transducer is driven to form a locally enhanced acoustic field within a predetermined frequency, so that the emitted light is controllably deflected in the Z direction perpendicular to the chip plane.

[0028] The beam, after being deflected in three dimensions, is coupled into free space to complete the scanning of the target area.

[0029] Furthermore, it also includes: applying a weighted window or phase encoding to the chirped interdigital transducer to suppress sidelobes; and performing pre-distortion compensation on the driving amplitude to keep the diffraction efficiency at different frequencies basically consistent.

[0030] Furthermore, it also includes: using on-chip monitoring optical path and detector to obtain real-time feedback, calibrating frequency-angle mapping relationship and temperature drift; and adopting segmented frequency sweep or segmented frequency jump mode between the low frequency band and the high frequency band to balance scanning speed and angular resolution.

[0031] Furthermore, the combination of two-dimensional scanning and Z-axis deflection is used to form a three-dimensional scanning system, which can be combined with frequency modulated continuous wave (FMCW) or time-of-flight (ToF) ranging systems.

[0032] This invention also provides a lidar system, including a light source; an optical path modulation module; an on-chip lidar chip based on acousto-optic modulation as described above; a driving and control circuit; and a receiving and signal processing module. The optical path modulation module is used to modulate the incident light so that the incident light can couple into the chip. The driving and control circuit is used to output programmable frequency, amplitude, and phase waveforms to multiple sets of interdigital transducers. The receiving and signal processing module is used to receive, photoelectrically convert, demodulate, and process the reflected light from the target, extract the target's distance, velocity, and reflection intensity information, and reconstruct a three-dimensional point cloud image. The system uses the chip to achieve dual-frequency broadband two-dimensional scanning and Z-axis deflection to complete three-dimensional environmental imaging.

[0033] Furthermore, the light source is a narrow linewidth tunable laser, and the system uses an FMCW (Frequency-Mechanical-Wave) system for distance and velocity measurement.

[0034] Furthermore, the receiving and signal processing module includes a coherent receiver or an avalanche photodiode array, and is synchronized with the driving and control circuit to achieve point cloud acquisition at a frame rate ≥ kHz.

[0035] Compared with the prior art, the beneficial effects of the present invention are:

[0036] 1. The present invention discloses an on-chip integrated laser radar based on acousto-optic modulation, which adopts a heterogeneous integrated structure of lithium niobate thin film layer and chalcogenide glass, resulting in high diffraction efficiency and low power consumption; through a dual-frequency broadband collaborative scanning mechanism of "large deflection in low frequency band" and "small deflection in high frequency band", it achieves the unification of large-range search and high-precision scanning; by integrating a dedicated focusing interdigital transducer to achieve Z-axis deflection, it realizes three-dimensional scanning function on a single integrated acousto-optic chip, with an extremely compact structure, avoiding the size, packaging and alignment problems caused by multi-chip stacking or external scanning modules.

[0037] 2. The on-chip acousto-optic scanning method of the present invention cleverly solves the inherent contradiction between the scanning field of view and angular resolution in a single AOD device by using a dual-frequency broadband collaborative scanning mechanism of "large deflection in the low-frequency band" and "small deflection in the high-frequency band", thus achieving the unification of large-range search and high-precision scanning; and realizes three-dimensional scanning function for the first time on a single integrated acousto-optic chip by using a focusing IDT to achieve Z-axis deflection. Attached Figure Description

[0038] Figure 1 This is a schematic diagram illustrating the principle of the on-chip integrated circuit structure of a lidar based on acousto-optic modulation.

[0039] Figure 2 This is a schematic diagram of the end face structure of an on-chip integrated circuit for a lidar system based on acousto-optic modulation.

[0040] Figure descriptions: 100, silicon layer; 200, silicon dioxide layer; 300, lithium niobate thin film layer; 400, chalcogenide glass waveguide layer; 500, interdigitated transducer. Detailed Implementation

[0041] The present invention will be further described below with reference to specific embodiments. The accompanying drawings are for illustrative purposes only, representing schematic diagrams rather than actual physical objects, and should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some components in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0042] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0043] Example 1

[0044] This embodiment is a first embodiment of a lidar on-chip integrated chip based on acousto-optic modulation, such as... Figure 1 and Figure 2 As shown, it includes:

[0045] An insulating substrate includes a silicon layer 100 and a silicon dioxide layer 200 located on the silicon layer 100;

[0046] Lithium niobate thin film layer 300 disposed on an insulating substrate;

[0047] A chalcogenide glass waveguide layer 400 is covered on a lithium niobate thin film layer 300. The chalcogenide glass waveguide layer 400 is etched to form an optical waveguide and an action region for acousto-optic interaction.

[0048] The device includes multiple sets of interdigital transducers 500, arranged above or adjacent to the active region, for exciting surface acoustic waves or Love waves in the composite structure composed of a lithium niobate thin film layer and a chalcogenide glass waveguide layer. These include at least two sets of apodization-weighted chirped interdigital transducers, with the acoustic wave propagation directions of the two sets of chirped interdigital transducers being non-collinear. They operate in preset high-frequency and low-frequency bands, respectively. By changing the driving frequency, the waveguide light undergoes Bragg diffraction in the active region and generates two-dimensional deflection, thereby achieving dual-frequency broadband two-dimensional scanning within the chip plane. It also includes at least one pair of focusing interdigital transducers, with the focusing direction pointing towards the light output path of the active region, for forming a focused acoustic field within the active region. This allows the beam, after two-dimensional deflection, to undergo controllable deflection in the Z direction perpendicular to the chip plane, thereby achieving three-dimensional scanning of the chip.

[0049] In this embodiment, a chalcogenide glass waveguide is heterogeneously integrated on an LNOI (lithium niobate on insulator) platform. The high voltage coefficient of lithium niobate is used to efficiently excite surface acoustic waves / Love waves, and the high acousto-optic coefficient and high refractive index of chalcogenide glass enable strongly coupled Bragg diffraction within the Love waveguide structure. Two sets of apodization-weighted chirped IDTs operate in low and high frequency bands respectively, corresponding to controllable frequency sweeps of "large angle—low frequency, small angle—high frequency," achieving continuous two-dimensional deflection and dual-frequency broadband splicing within the same frequency band. A focusing IDT directly opposite the output light is also provided to focus the sound field within the action region, cooperating with the output grating to achieve Z-axis deflection, thereby completing on-chip three-dimensional scanning. This invention possesses comprehensive advantages including inertia-free high speed, a wide field of view and fine resolution, high diffraction efficiency and extinction ratio, low RF power consumption, compact structure, and easy packaging, making it suitable for solid-state lidar based on FMCW or ToF systems.

[0050] In this embodiment, the electrode thickness of the interdigital transducer 500 is preferably 80 nm to 200 nm, enabling efficient excitation of surface acoustic waves in the frequency range of 80 MHz to 2 GHz. The chirped interdigital transducer simultaneously features electrode periodic chirping and electrode envelope weighting to broaden the acoustic bandwidth and suppress sidelobes. The electrode period of the chirped interdigital transducer is preferably 0.4 μm to 3 μm, corresponding to a center frequency of 0.8 GHz to 5 GHz. The focusing interdigital transducer has an arc-shaped, elliptical, or phase-encoded structure, used to form a locally enhanced acoustic field in the active region, causing controllable deflection of the emitted light in the Z direction perpendicular to the chip plane.

[0051] In this embodiment, multiple sets of interdigital transducers 500 are arranged in parallel according to frequency band segments, with each segment partially overlapping the others, so as to expand the total scanning bandwidth and field of view while maintaining high diffraction efficiency.

[0052] In this embodiment, the thickness of the chalcogenide glass waveguide layer 400 and the thickness of the lithium niobate thin film layer 300 satisfy the dispersion condition of the Love wave waveguide mode, so that the acoustic energy is coupled to the chalcogenide glass waveguide layer 400 and the optical mode is maximized to achieve overlap. The optical coupling between the chalcogenide glass waveguide layer 400 and the outside world adopts an output grating coupler. The period and tilt angle of the output grating are designed in coordination according to the acoustic wave vector scanning range to map the deflection in the waveguide to a large field of view in free space. The material of the chalcogenide glass waveguide layer 400 is one or more of As2S3, As2Se3, Ge–As–Se or Ge–Sb–Se; the lithium niobate thin film layer 300 is X-cut, Y-cut or 128°YX-cut oriented. The width of the chalcogenide optical waveguide is preferably 300 nm to 30 µm, and the height is preferably 200 nm to 500 nm to support single-mode or few-mode optical wave transmission in the communication band (e.g., 1550 nm C-band).

[0053] In this embodiment, acoustic absorption structures and / or bent acoustic waveguide structures are provided on both sides of the active region to reduce acoustic reflection and channel crosstalk. The acoustic absorption structure includes one or more of a polymer absorption layer, a micro / nano groove-type energy dissipation structure, or a porous dielectric layer, and is disposed on the outer periphery of the active region to suppress boundary reflection and crosstalk. At least two acousto-optic units are arranged in series along the light propagation direction in the active region, driven in a push-pull, in-phase, or out-of-phase manner, thereby improving the extinction ratio or diffraction efficiency.

[0054] In this embodiment, an impedance matching network, a power combining and distribution network, and a temperature compensation heater electrically connected to the interdigital transducer 500 are also included to stabilize the Bragg matching conditions.

[0055] In this embodiment, several of the above-mentioned chips can also be cascaded using waveguide couplers to form a scanning function with a wider range and greater angle. The waveguide coupler includes a multimode interference waveguide, a beam splitter, and photonic leads, etc.

[0056] like Figure 1 The figure shows a schematic diagram of the on-chip integrated circuit (ICC) of the lidar based on acousto-optic modulation in this embodiment. As shown, 1 represents the chalcogenide glass waveguide and the acousto-optic interaction region (the gray area where the etched optical waveguide / interaction cavity is located). 2 represents the optical path / output direction / output waveguide corresponding to the low-frequency band (blue indicates the outgoing or waveguide direction of this frequency band; it can be an output waveguide or connected to an outgoing grating). 3 represents the optical path / output direction / output waveguide corresponding to the high-frequency band (red indicates the outgoing or waveguide direction of this frequency band; it can be an output waveguide or connected to an outgoing grating). 4 represents one set of chirped IDTs (located below the chalcogenide glass waveguide and acousto-optic interaction region 1, exciting surface acoustic waves / Love waves, used as a reference acoustic axis for two-dimensional scanning). 5 represents another set of chirped IDTs (located above the chalcogenide glass waveguide and acousto-optic interaction region 1, arranged non-collinearly with 4, providing another reference acoustic axis; the two are combined to achieve two-dimensional vector scanning in the plane). 6 represents one of the focusing IDTs (located to the right of the chalcogenide glass waveguide and acousto-optic interaction region 1, directly facing the blue output light path 2, forming a focused acoustic field within the interaction region to cause the outgoing light to deflect in the Z direction). 7 represents another focusing IDT (located to the lower left of the chalcogenide glass waveguide and acousto-optic interaction region 1, directly facing the red output light path 3, forming a focused acoustic field within the interaction region to cause the outgoing light to deflect in the Z direction).

[0057] In the attached diagram, the coordinate system and colors are explained as follows: The X–Y coordinate system lies within the chip plane, and Z represents the chip normal. Blue beams represent low-frequency drive (larger deflection angle), and red beams represent high-frequency drive (smaller deflection angle). Angle and symbol explanation: θ: The instantaneous deflection angle in the X–Y plane (determined by the equivalent acoustic grating synthesized from two sets of chirped IDTs at a given frequency and phase). θ1: The center deflection angle of the low-frequency band (blue) in the X–Y plane; θ1±Δθ represents the angle range obtained by sweeping the frequency in this low-frequency band. θ3: The center deflection angle of the high-frequency band (red) in the X–Y plane; θ3±Δθ represents the angle range obtained by sweeping the frequency in this high-frequency band. Δθ: The amount of angle change caused by frequency sweeping within a certain frequency band, its magnitude determined by the sweep bandwidth and the effective acoustic aperture. θ2: After being focused by IDT 6, the Z-axis deflection angle of the blue beam relative to the chip plane (normal deflection when exiting free space). θ4: The Z-axis deflection angle of the red beam after being focused by IDT 7.

[0058] Working principle: Two sets of chirped IDTs 4 and 5 sweep frequencies in the low and high frequency bands respectively, forming acoustic wave vectors of different sizes. This causes the light in the two output waveguides 2 and 3 to undergo continuous Bragg diffraction in the X–Y plane and complete a two-dimensional scan (blue: θ1±Δθ; red: θ3±Δθ). Focusing IDTs 6 and 7 generate locally enhanced sound fields in the corresponding output directions, further deflecting the outgoing beam in the Z direction (θ2, θ4), thereby realizing the dual-frequency broadband two-dimensional scan and the three-dimensional scan function with Z-direction deflection.

[0059] The on-chip integrated circuit for lidar based on acousto-optic modulation provided in this embodiment has the following advantages:

[0060] 1. High diffraction efficiency and low power consumption: This invention innovatively employs a heterogeneous integrated structure of LNOI (lithium niobate on insulator) and chalcogenide glass. The high voltage coefficient of LNOI ensures the high efficiency of electro-acoustic conversion, while the excellent acousto-optic figure of merit of chalcogenide glass guarantees the high efficiency of acoustic-optic coupling. Combined with the strong confinement effect of Love waves on acoustic energy, diffraction efficiencies exceeding 50% or even higher can be achieved with relatively low RF drive power.

[0061] 2. Combining Wide Field of View and High Resolution: Through a dual-frequency broadband collaborative scanning mechanism of "large deflection in the low-frequency band" and "small deflection in the high-frequency band," this invention cleverly resolves the inherent contradiction between the scanning field of view and angular resolution in a single AOD device, achieving a balance between wide-range search and high-precision scanning. Simultaneously, the apodization-weighted IDT design effectively suppresses acoustic sidelobes, improving the resolution and extinction ratio of the scanned points.

[0062] 3. Single-chip 3D scanning: By integrating a dedicated focusing IDT to achieve Z-axis deflection, this invention is the first to realize 3D scanning function on a single integrated acousto-optic chip. The structure is extremely compact, avoiding the size, packaging and alignment problems caused by multi-chip stacking or external scanning modules.

[0063] 4. High scanning speed and high reliability: The acousto-optic scanning is a non-inertial scanning method with a response time on the order of microseconds, which is much faster than MEMS micromirrors. The all-solid-state design, without any moving mechanical parts, gives it extremely high shock and vibration resistance and long-term operational reliability.

[0064] 5. High integration and easy mass production: The overall structure of this invention is based on mature semiconductor micro-nano processing technology, which is easy to manufacture at the wafer level and can be integrated with other photonic devices such as on-chip lasers, detectors, and modulators, laying the foundation for realizing a fully integrated lidar system chip (SoC).

[0065] Example 2

[0066] This embodiment is an example of an on-chip acousto-optic scanning method. This embodiment uses the on-chip integrated chip for lidar based on acousto-optic modulation provided in Embodiment 1, including:

[0067] Laser in the communication band is coupled into the chalcogenide glass waveguide of the chip;

[0068] A programmable radio frequency (RF) signal source drives one set of chirped interdigital transducers in the low-frequency band (e.g., 80 MHz ~ 500 MHz) and / or alternately drives another set of chirped interdigital transducers in the high-frequency band (e.g., 500 MHz ~ 2 GHz). The magnitude and direction of the acoustic wave vector are controlled by continuous frequency sweeping or frequency hopping. Frequency sweeping changes the magnitude of the acoustic wave vector of the two sets of chirped interdigital transducers, and time-division multiplexing or frequency-division multiplexing is performed between the two sets of chirped interdigital transducers. By adjusting the relative amplitude and phase of the two sets of chirped interdigital transducers, an equivalent acoustic grating of the target vector is synthesized, thereby achieving two-dimensional in-plane deflection within the waveguide.

[0069] According to the requirements of 3D scanning, the driving focused interdigital transducer forms a local enhanced sound field within a predetermined frequency, so that the emitted light is controllably deflected in the Z direction perpendicular to the chip plane.

[0070] The beam, after being deflected in three dimensions, is coupled into free space to complete the scanning of the target area.

[0071] In this embodiment, the method further includes: applying a weighted window or phase encoding to the chirped interdigital transducer to suppress sidelobes; and performing pre-distortion compensation on the driving amplitude to keep the diffraction efficiency at different frequencies basically consistent.

[0072] In this embodiment, the method further includes: using on-chip monitoring optical path and detector to obtain real-time feedback, calibrating frequency-angle mapping relationship and temperature drift; and adopting segmented frequency sweep or segmented frequency jump mode between low frequency band and high frequency band to balance scanning speed and angular resolution.

[0073] In this embodiment, the combination of two-dimensional scanning and Z-axis deflection is used to form a three-dimensional scanning system, which can be combined with frequency modulated continuous wave (FMCW) or time-of-flight (ToF) ranging systems.

[0074] This embodiment provides an on-chip acousto-optic scanning method that solves the inherent contradiction between the scanning field of view and angular resolution in a single AOD device by using a dual-frequency broadband collaborative scanning mechanism of "large deflection in the low-frequency band" and "small deflection in the high-frequency band," thus achieving a unification of large-range search and high-precision scanning. By using a focusing IDT to achieve Z-axis deflection, a three-dimensional scanning function is realized on a single integrated acousto-optic chip.

[0075] Example 3

[0076] This embodiment is an example of a lidar system, including a light source; an optical path modulation module; an on-chip integrated lidar chip based on acousto-optic modulation as described in Embodiment 1; a driving and control circuit; and a receiving and signal processing module. The optical path modulation module is used to modulate the incident light so that the incident light can couple into the chip. The driving and control circuit is used to output programmable frequency, amplitude, and phase waveforms to multiple sets of interdigital transducers. The receiving and signal processing module is used to receive, photoelectrically convert, demodulate, and process the reflected light from the target, extract the target's distance, velocity, and reflection intensity information, and reconstruct a three-dimensional point cloud image. The system uses the chip to achieve dual-frequency broadband two-dimensional scanning and Z-axis deflection to complete three-dimensional environmental imaging.

[0077] In this embodiment, the light source is a narrow linewidth tunable laser, and the system uses an FMCW (Frequency-Mechanical-Wave) system for distance and velocity measurement.

[0078] In this embodiment, the receiving and signal processing module includes a coherent receiver or an avalanche photodiode array, and is synchronized with the driving and control circuit to achieve point cloud acquisition at a frame rate ≥ kHz.

[0079] The working principle is as follows: When the system is working, the laser emitted by the light source is shaped by the optical path modulation module and coupled into the chalcogenide glass waveguide of the chip. The drive and control circuit outputs programmable sweep signals to two sets of chirped interdigital transducers according to the scanning requirements, realizing two-dimensional deflection of the beam in the X–Y plane within the waveguide. Simultaneously, a specific frequency radio frequency signal is applied to the focusing interdigital transducer, forming a focused sound field in the action area, causing the beam to deflect in the Z direction, thereby achieving three-dimensional spatial scanning. The scanning beam is coupled into free space through the output grating, illuminating the target object and reflecting back. The reflected light is captured by the receiving module, and after photoelectric conversion and signal processing, combined with the scanning angle information, a three-dimensional point cloud image of the target is reconstructed.

[0080] In the specific implementation of the above embodiments, the technical features can be combined in any non-contradictory way. For the sake of brevity, not all possible combinations of the above technical features are described. However, as long as the combination of these technical features is not contradictory, it should be considered to be within the scope of this specification.

[0081] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A lidar on-chip integrated chip based on acousto-optic modulation, characterized in that, include: Insulating substrate; A lithium niobate thin film layer disposed on an insulating substrate; A chalcogenide glass waveguide layer is covered on the lithium niobate thin film layer, and the chalcogenide glass waveguide layer is etched to form an optical waveguide and an action region for acousto-optic interaction; The system includes multiple sets of interdigital transducers arranged above, below, or adjacent to the active region to excite surface acoustic waves or Love waves in the composite structure composed of the lithium niobate thin film layer and the chalcogenide glass waveguide layer. These include at least two sets of apodization-weighted chirped interdigital transducers, whose acoustic wave propagation directions are non-collinear. They operate in preset high-frequency and low-frequency bands, respectively. By changing the driving frequency, the waveguide light undergoes Bragg diffraction in the active region, generating a two-dimensional deflection, thereby achieving dual-frequency broadband two-dimensional scanning within the chip plane. It also includes at least one pair of focusing interdigital transducers, with the focusing direction pointing towards the light output path of the active region, to form a focused acoustic field within the active region. This causes the beam, after two-dimensional deflection, to deflect in the Z direction perpendicular to the chip plane, thereby achieving three-dimensional scanning of the chip.

2. The on-chip integrated circuit for lidar based on acousto-optic modulation according to claim 1, characterized in that, The chirped interdigital transducer has both electrode periodic chirping and electrode envelope weighting to broaden the acoustic bandwidth and suppress side lobes; the focusing interdigital transducer is an arc-shaped, elliptical, or phase-coded structure used to form a locally enhanced acoustic field in the active area, so that the emitted light is deflected in a controllable manner in the Z direction perpendicular to the chip plane.

3. The on-chip integrated circuit for lidar based on acousto-optic modulation according to claim 1, characterized in that, The thickness of the chalcogenide glass waveguide layer and the thickness of the lithium niobate thin film layer satisfy the dispersion condition of the Love wave waveguide mode, so that the acoustic energy is coupled to the chalcogenide glass waveguide layer and the optical mode is maximized to achieve overlap. The optical coupling between the chalcogenide glass waveguide layer and the outside world adopts an output grating coupler. The period and tilt angle of the output grating are designed in coordination according to the acoustic wave vector scanning range, so as to map the deflection in the waveguide into a large field of view scanning in free space.

4. The on-chip integrated circuit for lidar based on acousto-optic modulation according to claim 1, characterized in that, Acoustic absorption structures and / or bent acoustic waveguide structures are provided on both sides of the active region to reduce acoustic reflection and channel crosstalk; at least two acousto-optic units are connected in series in the active region along the light propagation direction and driven in a push-pull, in-phase or out-of-phase manner to improve the extinction ratio or diffraction efficiency.

5. The on-chip integrated circuit for lidar based on acousto-optic modulation according to claim 1, characterized in that, Multiple sets of interdigital transducers are arranged in parallel according to frequency band segments, with each segment partially overlapping the others, in order to expand the total scanning bandwidth and field of view while maintaining high diffraction efficiency.

6. The on-chip integrated circuit for lidar based on acousto-optic modulation according to any one of claims 1 to 5, characterized in that, It also includes an impedance matching network, a power combining and distribution network, and a temperature compensation heater that are electrically connected to the interdigital transducer to stabilize the Bragg matching conditions.

7. An on-chip acousto-optic scanning method, characterized in that, The on-chip integrated circuit for lidar based on acousto-optic modulation as described in any one of claims 1 to 6 comprises: One set of the chirped interdigital transducers is driven in the low-frequency band; the other set of the chirped interdigital transducers is driven in the high-frequency band; the acoustic wave vector magnitudes of the two sets of chirped interdigital transducers are changed by frequency sweep, and time division multiplexing or frequency division multiplexing is performed between the two sets of chirped interdigital transducers; by adjusting the relative amplitude and phase of the two sets of chirped interdigital transducers, an equivalent acoustic grating of the target vector is synthesized, thereby realizing two-dimensional deflection in the plane within the waveguide; The focused interdigital transducer is driven to form a locally enhanced acoustic field within a predetermined frequency, causing the emitted light to deflect in the Z direction perpendicular to the chip plane. The beam, after being deflected in three dimensions, is coupled into free space to complete the scanning of the target area.

8. The on-chip acousto-optic scanning method according to claim 7, characterized in that, Also includes: A weighted window or phase coding is applied to the chirped interdigital transducer to suppress sidelobes; Furthermore, pre-distortion compensation is performed on the driving amplitude to ensure that the diffraction efficiency remains consistent at different frequencies.

9. The on-chip acousto-optic scanning method according to claim 7, characterized in that, It also includes: using on-chip monitoring optical path and detector to obtain real-time feedback, calibrating frequency-angle mapping relationship and temperature drift; and adopting segmented frequency sweep or segmented frequency jump mode between the low frequency band and the high frequency band to balance scanning speed and angular resolution.

10. A lidar system, characterized in that, Includes a light source; an optical path modulation module; an on-chip integrated circuit for a lidar based on acousto-optic modulation as described in any one of claims 1 to 6; a driving and control circuit; and a receiving and signal processing module; The optical path modulation module is used to modulate the incident light so that the incident light can couple into the chip. The driving and control circuit is used to output programmable frequency, amplitude and phase waveforms to multiple sets of interdigital transducers. The receiving and signal processing module is used to receive, photoelectrically convert, demodulate and process the reflected light from the target, extract the target's distance, velocity and reflection intensity information, and reconstruct a three-dimensional point cloud image. The lidar system uses the chip to achieve dual-frequency broadband two-dimensional scanning and Z-axis deflection to complete three-dimensional environmental imaging.

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