On-chip light beam scanning device and method based on refraction effect

Abstract

The invention discloses an on-chip light beam scanning device and method based on a refraction effect. The on-chip light beam scanning device comprises a light source input area, a spot-size conversion area (which is determined according to a required light spot divergence angle and is not necessary), a refraction area and a grating emission area, signal light can be input in the light source input area in an external light source coupling mode, and an on-chip light source scheme can also be adopted; the spot size of the input light is adjusted by the spot conversion area; the refraction area adjusts the propagation direction of a wave beam by means of a refraction principle; and the grating area converts the adjusted and steered optical signal into spatial light and emits the spatial light to the space. The method has the advantages that forming and steering of wave beams are achieved through a simple structure and single drive, emitted light spots do not have side lobes or grating lobes, target recognition confusion is avoided, and meanwhile main lobe energy is improved. In addition, due to the fact that the wide waveguide area in the whole process can bear the extremely high optical power upper limit, the on-chip transmitting power may reach the watt magnitude. The whole scheme is a pure solid-state scheme, the manufacturing cost is low, and the reliability is high.

Description

Technical Field

[0001] This invention relates to the field of beam scanning technology, and more specifically to an on-chip beam scanning device and method based on refraction effects. Background Technology

[0002] Light detection and ranging (Lidar) can provide relatively long-distance and high-precision 3D imaging, which is crucial for future autonomous vehicles. Beam deflection technology, as a key technology of Lidar, has always been a hot research topic. The current mainstream beam deflection technologies can be divided into four types according to their technical paths: (1) Mechanical structures that achieve steering by means of motors are currently the most widely used technical solutions for vehicle-mounted LiDAR due to their high maturity, but they also have disadvantages such as large size, low reliability, and high cost; (2) MicroElectroMechanical Systems (MEMS) mainly use electrostatic, magnetic, thermal, piezoelectric and other driving methods to control the structure in the chip, such as the mirror, which is usually on the order of mm; Compared with traditional mechanical structures, the resonant frequency of MEMS is much higher than that of the vehicle, which enhances robustness. Its disadvantage of small deflection angle can be overcome by the method of multiple channel fusion. At present, many companies regard MEMS solutions as one of the preferred solutions for LiDAR. (3) Liquid crystal phased array technology refers to controlling the refractive index of the liquid crystal layer by applying an external electric field, so that the liquid crystal layer at different positions has different refractive indices. Its disadvantage is that the scanning speed is relatively slow. (4) On-chip pure solid-state solutions can be further divided into optical phase array (OPA) and focal plane switch array (FPSA). FPSA uses lenses to edit the wavefront phase. Its structure is simple, but its non-reprogrammable characteristic determines that it is essentially a discrete scan, and blind spots are difficult to avoid. At the same time, due to the limitations of the lens, the deflection angle of the FPSA solution is generally small (generally less than 40 degrees). Although OPA is currently the most popular future-oriented beam deflection technology, its complex control system and large on-chip loss greatly limit its application in the commercial field.

[0003] While pure solid-state lidar has long been highly anticipated by the industry, mechanically scanned lidar, characterized by its large size, high cost, and poor stability, still dominates the market. The core reason is that current pure solid-state solutions still suffer from numerous problems. For LiDAR to achieve large-scale application in the industry, a small, simple-to-drive, low-loss, and high-power-tolerance pure solid-state beam deflection solution is urgently needed. Summary of the Invention

[0004] This invention addresses the problems of high control complexity, blind zone, and high on-chip loss in existing pure solid-state beam scanning technologies. It proposes a novel pure solid-state on-chip two-dimensional beamforming and scanning scheme based on the refraction effect of light, which has advantages such as low control complexity, simple structure, low on-chip loss, single beam emission without sidelobes or gratings, and continuous scanning without blind zones.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The present invention provides an on-chip beam scanning device based on the refraction effect, characterized in that it includes a light source input area, a mode conversion area, a refraction area and a grating emission area integrated on the same substrate and arranged sequentially. The light source input area uses either external light source coupling or on-chip light source integration to input signal light; The mode conversion region is used to transform the mode size of the input optical signal; The refractive region includes an optical waveguide transmission channel and an active control structure disposed on the transmission channel. The active control structure can form a medium region with adjustable refractive index within the local waveguide region it covers. By controlling the working state of the active control structure, the refractive index of the medium region can be adjusted, so that the light beam transmitted through the region can be continuously and tunably deflected in the propagation direction based on the principle of refraction. The grating emission region includes a diffraction structure for coupling light within the waveguide to free space; the beam deflected by the refraction region is incident on the grating emission region at a controllable angle, and after interacting with the diffraction structure, it radiates into free space in a corresponding direction, thereby achieving scanning control of the beam direction.

[0006] Preferably, the optical waveguide transmission channel in the refractive region is a planar waveguide, and its width gradually changes along the optical transmission direction.

[0007] Preferably, the light source area can be coupled with an external light source or integrated with an on-chip light source, such as end-face coupling, grating coupling, heterogeneous integration, hybrid integration, and on-chip light source.

[0008] Preferably, the mode conversion region can be a conventional linear or nonlinear conical mode converter, or a novel solution utilizing an on-chip lens, etc.

[0009] Preferably, the refractive region can utilize thermo-optical, electro-optical, acousto-optical, all-optical, or even liquid crystal technologies to generate single or multiple cascaded triangular regions with adjustable intensity for light refraction, thereby changing the beam propagation direction.

[0010] Preferably, the grating region, depending on the incident beam angle and wavelength, experiences constructive or destructive interference at different locations when propagating into free space, thereby achieving beam scanning.

[0011] Preferably, the waveguide surface material used in the array waveguide is silicon, silicon nitride, or III-V material.

[0012] Compared with the prior art, the present invention has the following beneficial effects: 1. The refraction effect is introduced into the on-chip beam deflection technology. The beam is deflected in the planar waveguide by adjusting the refractive index of the refractive region. After deflection, the beam is emitted to different azimuth angles in space by the grating. 2. Compared with traditional mechanical beam deflection schemes, this scheme is a pure solid-state technology, which can significantly improve reliability, reduce size and power consumption, and has the key advantages of high speed and flexibility and continuous blind-zone-free scanning. 3. Compared with traditional solid-state deflection technology, it does not require the complex driving mechanism of optical phased arrays, nor does it suffer from side lobes or grating lobes. Moreover, due to its simple structure, its on-chip loss is much lower than that of phased arrays. Compared with traditional focal plane gating arrays, it is a continuous scanning system with no blind spots. Its driving mechanism is simple, and its structure does not require complex switching arrays or off-chip lens systems, which can greatly reduce the size of the device. 4. By cascading multiple refractive regions and rationally designing the shape of the refractive regions, the requirement for the amount of refractive index change in the refractive regions can be reduced; 5. It has many advantages such as low cost, simple design, CMOS compatibility, pure solid-state, high robustness, high power tolerance, large scanning angle, and low driving complexity. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the on-chip beam scanning device based on the refraction effect of the present invention.

[0014] Figure 2 It is the far-field diffraction pattern of the grating after changing the refractive index of the refractive region. Detailed Implementation

[0015] The present invention will now be further described with reference to the embodiments and the accompanying drawings.

[0016] Example like Figure 1 As shown, the device is integrated on the same silicon substrate and mainly consists of a light source input area (end-face coupling area), a mode conversion area (linear tapered waveguide), a refraction area (a triangular thermo-optic control area containing heating electrodes), and a grating emission area (uniform periodic grating).

[0017] The light source input area can be coupled with an external light source or integrated with an on-chip light source, such as end-face coupling, grating coupling, heterogeneous integration, hybrid integration, and on-chip light source, as long as the light can be delivered to the mode conversion area.

[0018] The mode conversion region is essential under most conditions because the divergence angle of the outgoing beam is related to the size of the input mode. The design of the mode conversion region is not limited; it can be a conventional linear or nonlinear conical mode converter, or a novel solution using an on-chip lens. Figure 1 The diagram shows a scheme for achieving pattern conversion through coupling.

[0019] The refractive region is also the on-chip beam steering region. The main structure utilizes thermo-optical, electro-optical, acousto-optical, all-optical, or even liquid crystal technologies to generate an intensity-adjustable beam-direction tuning region for light refraction. Figure 1 The image shows a scheme that uses a single triangular tuning region to achieve refraction deflection through a thermo-optical approach.

[0020] For the emission region, if it is used for one-dimensional beam deflection, the end face is generally sufficient. If two-dimensional beam deflection is required, the region can be designed as a grating scheme, and there are no restrictions on the shape of the grating or the intensity of the disturbance. Figure 1 The diagram shows a non-deflection two-dimensional beam deflection scheme, also known as a grating scheme, which is mainly used to project beams into free space. The waveguide materials used here include, but are not limited to, silicon, silicon nitride, and III-V materials.

[0021] The workflow of this embodiment: 1. The signal light is input through the input port in the light source input area.

[0022] 2. In the pattern transition zone, such as Figure 1 In the scheme shown, the fundamental mode of a small beam is converted into the fundamental mode of a large beam through evanescent wave coupling. The divergence angle of the emitted beam is strongly correlated with the beam size, so the mode converter needs to be designed reasonably according to the required divergence angle and the size of the incident beam to couple the light into different waveguides through the connecting region.

[0023] 3. The light beam enters the refraction region from the mode conversion region. The refraction region mainly consists of two parts: a tapered planar waveguide for transmitting the light field and an active region for changing the refractive index of the planar waveguide. A tapered planar waveguide is used because the light beam deflects here, preventing energy leakage and reflection at the waveguide sidewalls that could affect the electric field distribution. The active region is triangular in shape to refract the beam twice, reducing the need for a change in refractive index. In practical applications, the tilt angle of the refracting surfaces, the number of refracting surfaces, and the change in refractive index determine the beam deflection and the emission direction of the exit angle.

[0024] 4. After passing through the refraction zone, the light beam is incident on the grating emission zone at a certain angle. Due to the angle between the incident beam and the normal to the perturbation plane, the exit angle of the emitted beam deflects in both the vertical and horizontal directions compared to the incident light. The vertical deflection angle mainly depends on the angle between the incident beam and the perturbation plane of the grating region, as well as the effective refractive index of the grating region. The horizontal deflection angle mainly depends on the wavelength of the incident beam. In other words, the vertical direction of the emitted beam is adjusted by regulating the refraction intensity of the refraction zone, and the horizontal direction is adjusted by changing the wavelength of the incident light source.

[0025] In another embodiment, the active control unit in the refractive region can employ an electro-optic effect based on carrier injection. By applying a reverse bias voltage within the triangular region of the PN junction or PIN junction structure, the carrier concentration is changed, thereby rapidly modulating the refractive index (response time can reach the nanosecond level).

[0026] The grating emission region can also be designed as a non-uniform grating (such as a chirped grating or a focusing grating) to further control the beam shape or achieve a specific field distribution.

[0027] The mode conversion region can be achieved with high-efficiency conversion using structures such as multimode interference (MMI) couplers or adiabatic directional couplers.

[0028] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and additions without departing from the principle of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention.

Claims

1. An on-chip beam scanning device based on refraction effect, characterized in that: It includes a light source input area, a mode conversion area, a refractive area, and a grating emission area, which are integrated on the same substrate and arranged sequentially. The light source input area uses either external light source coupling or on-chip light source integration to input signal light; The mode conversion region is used to transform the mode size of the input optical signal; The refractive region includes an optical waveguide transmission channel and an active control structure disposed on the transmission channel. The active control structure can form a medium region with adjustable refractive index within the local waveguide region it covers. By controlling the working state of the active control structure, the refractive index of the medium region can be adjusted, so that the light beam transmitted through the region can be continuously and tunably deflected in the propagation direction based on the principle of refraction. The grating emission region includes a diffraction structure for coupling light within the waveguide to free space; the beam deflected by the refraction region is incident on the grating emission region at a controllable angle, and after interacting with the diffraction structure, it radiates into free space in a corresponding direction, thereby achieving scanning control of the beam direction.

2. The on-chip beam scanning device based on refraction effect according to claim 1, characterized in that: The optical waveguide transmission channel in the refractive region is a planar waveguide, and its width gradually changes along the optical transmission direction.

3. The on-chip beam scanning device based on refraction effect according to claim 1 or 2, characterized in that: The active control structure is configured to form one or more refractive index control regions with a triangular cross-sectional shape within the waveguide region.

4. The on-chip beam scanning device based on refraction effect according to claim 3, characterized in that: The refractive index control region of the triangle constitutes an on-chip integrated prism structure with dynamically tunable refractive index.

5. The on-chip beam scanning device based on refraction effect according to claim 1, characterized in that: The active control structure modulates the refractive index of the medium region based on the thermo-optic effect, electro-optic effect, acousto-optic effect, all-optic effect, or the electro-optic effect of liquid crystal.

6. The on-chip beam scanning device based on refraction effect according to claim 5, characterized in that: When the active control structure is based on the thermo-optic effect, it includes a heating electrode covering the waveguide region; by controlling the current or voltage applied to the heating electrode, the temperature and corresponding refractive index of the dielectric region are changed.

7. The on-chip beam scanning device based on refraction effect according to claim 5, characterized in that: When the active modulation structure is based on the electro-optic effect, it forms a semiconductor modulation region with a PN junction or PIN junction structure in the waveguide region; by applying a bias voltage to the modulation region, the carrier concentration and the corresponding refractive index are changed.

8. The on-chip beam scanning device based on refraction effect according to claim 1, characterized in that, Two-dimensional scanning of the beam emitted from the grating emission region is achieved by independently controlling at least one of the following parameters: (a) adjusting the angle at which the beam is incident on the grating emission region by controlling the refractive index of the refractive region, thereby controlling the beam's emission direction in the pitch dimension; (b) controlling the wavelength of the light signal input to the light source input region, thereby controlling the beam's emission direction in the azimuth dimension.

9. The on-chip beam scanning device based on refraction effect according to claim 1, characterized in that, The refractive region includes multiple independent controllable refractive units cascaded along the optical path, and each refractive unit is provided with an independent active control structure.

10. An on-chip beam scanning method based on refraction effect, characterized in that, The apparatus of any one of claims 1 to 9 comprises: The optical signal is introduced from the light source input area into the waveguide structure; The optical signal undergoes mode size conversion through the mode conversion region; By controlling the active modulation structure in the refractive region, a medium region with an adjustable refractive index is formed in a local area of ​​the waveguide, so that the light beam passing through the region undergoes continuous directional deflection based on refraction. The deflected beam is guided into the grating emission region and coupled to free space through the diffraction structure; By adjusting the refractive index of the refractive region, the incident angle of the light beam in the grating emission region is changed, thereby achieving continuous scanning of the emitted light beam in one dimension. And / or, by changing the wavelength of the optical signal, the wavelength dispersion characteristics of the grating emission region are utilized to achieve scanning of the emitted beam in another dimension, or to complete a two-dimensional scan in conjunction with the aforementioned one-dimensional scan.

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