Wavelength scanning high-power silicon nitride focal plane array laser radar transmitter

Abstract

The invention discloses a wavelength-scanning high-power silicon nitride focal plane array laser radar transmitter, and belongs to the field of laser radars and optical waveguide integrated devices. The problem that an existing laser radar transmitting structure is limited in bearing power and not suitable for long-distance detection is solved, a tunable laser generates optical signals with different wavelengths, and the optical signals are coupled into a waveguide through an edge coupler and transmitted into a wavelength division multiplexer through the waveguide; the wavelength division multiplexer sends the optical signal to a bus waveguide corresponding to the optical antenna array according to the wavelength of the received optical signal; the optical antenna array comprises n bus waveguides, and grating couplers on the n bus waveguides are correspondingly arranged to form an n-row m-column antenna array; and an off-chip aspherical lens is arranged above the optical antenna array and is used for carrying out light beam collimation and emission angle modulation on optical signals emitted by the optical antennas. The laser radar transmitter is suitable for being used as a laser radar transmitter.

Description

Technical Field

[0001] The invention belongs to the field of laser radar and optical waveguide integrated devices. Background Art

[0002] With the rapid development of intelligent unmanned systems, LiDAR has been widely used as a key sensor in the fields of autonomous driving, robot navigation and high-precision mapping. Focal plane switch array (FPSA) is a new type of beam scanning technology that can use lenses to establish an accurate correspondence between the output beam direction and the position of the array antenna unit. By switching different transmitting units in the array, FPSA can achieve directional scanning of the beam without mechanical movement. At present, most designs for this system are designed and processed based on silicon waveguides, and then assisted by optical switches to control them. However, this design has limited carrying power and is not suitable for long-distance detection. In addition, the introduction of optical switches increases the overall complexity and optical loss of the chip. Summary of the invention

[0003] The present invention aims to solve the problem that the existing laser radar transmitting structure has limited carrying power and is not suitable for long-distance detection. A high-power silicon nitride focal plane array laser radar transmitter with wavelength scanning is provided.

[0004] The wavelength-scanning high-power silicon nitride focal plane array laser radar transmitter of the present invention comprises: a tunable laser, an edge coupler, a wavelength division multiplexer, an optical antenna array and an off-chip aspheric lens;

[0005] The tunable laser is used to generate optical signals of different wavelengths. The optical signals are coupled into the waveguide through the edge coupler, and are transmitted into the wavelength division multiplexer through the waveguide. The wavelength division multiplexer sends the optical signals to the optical antennas corresponding to the optical antenna array according to the wavelengths of the received optical signals.

[0006] The optical antenna array comprises n bus waveguides, each bus waveguide is connected to m arbitrary splitting ratio devices, each arbitrary splitting ratio device is connected to a grating coupler; the grating couplers on the n bus waveguides are arranged correspondingly to form an antenna array with n rows and m columns;

[0007] An off-chip aspheric lens is provided above the optical antenna array, and the off-chip aspheric lens is used to collimate the light beam and modulate the emission angle of the optical signal emitted by the optical antenna.

[0008] Furthermore, the present invention also includes a driving circuit, and the driving circuit is used to drive the tunable laser.

[0009] Furthermore, in the present invention, the grating coupler is connected to the bus waveguide via an arbitrary splitting ratio device.

[0010] Furthermore, in the present invention, the wavelength division multiplexer is implemented by using an arrayed waveguide grating or a cascaded multi-mode interferometer.

[0011] Furthermore, in the present invention, the optical antenna array is used for coupling the waveguide mode to the free space mode.

[0012] Furthermore, in the present invention, the splitting ratios of any splitting ratio device from the input end to the output end of the bus waveguide light are 1 / m, 1 / (m-1), 1 / (m-2)...1 respectively.

[0013] Furthermore, in the present invention, the edge coupler is a wide wavelength edge coupler.

[0014] Furthermore, the present invention also includes a silicon nitride substrate, and the optical antenna array is arranged on the upper surface of the silicon nitride substrate.

[0015] Furthermore, in the present invention, the edge coupler, the wavelength division multiplexer and the optical antenna array are an integrated structure, and the integrated structure is photolithographically formed on a silicon nitride waveguide layer of a silicon nitride substrate, and the silicon nitride substrate includes, from bottom to top, a silicon base layer, a silicon dioxide buffer layer, a silicon nitride waveguide layer and a silicon dioxide cladding layer.

[0016] The present invention provides a wavelength-scanning high-power silicon nitride focal plane array laser radar transmitter. Compared with other laser radar transmitters, the present invention does not require any on-chip active devices, and can achieve the effect of two-dimensional modulation of the emission beam by simply changing the incident wavelength, greatly reducing the complexity of the chip and the control difficulty of the drive circuit. Moreover, the present invention is designed based on silicon nitride waveguides, and the overall transmission power has been greatly improved, which can be directly used in long-distance laser detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The schematic diagram of the high-power silicon nitride focal plane array laser radar transmitter for wavelength scanning according to the present invention;

[0018] Figure 2 is a schematic diagram of the substrate layered structure;

[0019] Figure 3 Spectra of grating coupler at different wavelengths;

[0020] Figure 4 It is a schematic diagram of the structure when the wavelength division multiplexing device adopts cascaded MM;

[0021] Figure 5 This is a schematic diagram of the structure when the wavelength division multiplexing device uses AWG;

[0022] Figure 6Schematic diagram of the structure of a very large-scale transmitting array. DETAILED DESCRIPTION

[0023] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0024] Specific implementation method 1: refer to Figure 1 Specifically describing this embodiment, the wavelength-scanning high-power silicon nitride focal plane array laser radar transmitter described in this embodiment includes: a tunable laser 1, an edge coupler 3, a wavelength division multiplexer 4, an optical antenna array 5 and an off-chip aspheric lens 6;

[0025] The tunable laser 1 is used to generate optical signals of different wavelengths. The optical signals are coupled into the waveguide via the edge coupler 3, and are transmitted into the wavelength division multiplexer 4 via the waveguide. The wavelength division multiplexer 4 sends the optical signals to the optical antennas corresponding to the optical antenna array 5 according to the wavelengths of the received optical signals.

[0026] The optical antenna array 5 comprises n bus waveguides, each bus waveguide is connected to m arbitrary splitting ratio devices 7, and each arbitrary splitting ratio device 7 is connected to a grating coupler 8; the grating couplers 8 on the n bus waveguides are arranged correspondingly to form an antenna array with n rows and m columns;

[0027] An off-chip aspheric lens 6 is provided above the optical antenna array 5 , and the off-chip aspheric lens 6 is used to collimate the light beam and modulate the emission angle of the optical signal emitted by the optical antenna.

[0028] Furthermore, the present invention further comprises a driving circuit 2 , and the driving circuit 2 is used to drive the tunable laser 1 .

[0029] Furthermore, in this embodiment, the grating coupler 8 is connected to the bus waveguide via the arbitrary splitting ratio device 7 .

[0030] Furthermore, in this embodiment, the wavelength division multiplexer 4 is implemented by an arrayed waveguide grating or a cascaded multi-mode interferometer.

[0031] Furthermore, in this embodiment, the optical antenna array 5 is used for coupling the waveguide mode to the free space mode.

[0032] Furthermore, in this embodiment, the splitting ratios of any splitting ratio device from the input end to the output end of the bus waveguide light are 1 / m, 1 / (m-1), 1 / (m-2)...1 respectively.

[0033] Furthermore, in this embodiment, the edge coupler 3 is a wide wavelength edge coupler.

[0034] Furthermore, in this embodiment, a silicon nitride substrate is also included, and the optical antenna array 5 is arranged on the upper surface of the silicon nitride substrate.

[0035] Furthermore, in this embodiment, the edge coupler 3, the wavelength division multiplexer 4 and the optical antenna array 5 are an integrated structure, and the integrated structure is photolithographically formed on a silicon nitride waveguide layer 030 of a silicon nitride substrate, and the silicon nitride substrate includes, from bottom to top, a silicon base layer 010, a silicon dioxide buffer layer 020, a silicon nitride waveguide layer 030 and a silicon dioxide cladding layer 040.

[0036] The high-power silicon nitride focal plane array laser radar transmitter based on the wavelength scanning of the silicon nitride substrate is manufactured by using the substrate. The substrate is composed of a 2mm silicon base 010 layer, a 2um thick silicon dioxide buffer layer, a 400nm silicon nitride waveguide layer and a 4um thick silicon dioxide cladding layer from bottom to top. Figure 2 shown.

[0037] like Figure 1 The figure shows the structure of a wavelength-scanning high-power silicon nitride focal plane array lidar transmitter. It includes an edge coupler, a wavelength division multiplexer, an arbitrary splitting ratio power divider, and an optical antenna array. The edge coupler uses a wavelength-insensitive wide-wavelength edge coupler to couple incident light of different wavelengths emitted by the fiber laser. The wavelength division multiplexer can use structures such as AWG and cascaded MMI, and can transmit the incident light to the corresponding waveguide bus according to its wavelength, i.e., λ1, λ2, ... λ in the figure. n The corresponding waveguide bus in the y direction is realized by wavelength division multiplexing. The arbitrary splitting ratio power splitter can use a directional coupler or a beam splitter with MMI as the basic structure to divide the energy of the bus waveguide into mode field lights of the same energy in turn and output them to the subsequent grating coupler; the optical antenna array uses a grating coupler for output and is individually designed according to the wavelength of each row to ensure that the central wavelength of the grating coupler is consistent with the corresponding wavelength, such as Figure 3 As shown in the figure, the light coupled into the free space by the grating coupler can be emitted at different angles after passing through the off-chip lens, thus realizing scanning in the x direction through space division multiplexing.

[0038] For wavelength division multiplexing devices, when the transmitting array is relatively small, a cascaded MMI structure is generally used as a wavelength division multiplexing device, such as Figure 4As shown; when the transmitting array is large, for example, the number of arrays is 64×64 or 128×128, AWG can generally be used as a wavelength division multiplexing device, such as Figure 5 As shown; when the transmitting array needs to be larger, it is necessary to use two or more wavelength division multiplexing devices, and add a corresponding number of wide wavelength wavelength division multiplexing devices before the wavelength division multiplexing device to roughly divide it before performing wavelength addressing operations, such as Figure 6 shown.

[0039] Combination Figure 1 The specific process of implementing scanning in this embodiment is as follows:

[0040] (1) The driving circuit controls the tunable fiber laser to emit light with a wavelength of λ1;

[0041] (2) The edge coupler couples the corresponding outgoing light into the waveguide layer;

[0042] (3) The light coupled into the waveguide layer is transmitted to the first row of bus waveguides according to the relationship between the bus waveguide port and the wavelength after passing through the wavelength division multiplexing device;

[0043] (4) The light transmitted to the bus waveguide passes through four power dividers and is then transmitted to the grating coupler with equal energy;

[0044] (5) Grating couplers at different positions radiate into free space and are deflected at four different angles after being incident on an off-chip lens, completing a scanning effect in the x-direction;

[0045] (6) Changing the driving circuit so that the emission wavelength of the fiber laser is λ2;

[0046] (7) Repeat the process of (2)-(5), except that the bus waveguide is now in the second row, achieving a scanning result in the y direction.

[0047] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. It should therefore be understood that many modifications may be made to the exemplary embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in a manner different from that described in the original claims. It should also be understood that the features described in conjunction with a single embodiment may be used in other described embodiments.

Claims

1. Wavelength-scanned high-power silicon nitride focal plane array lidar transmitter, characterized in that: include: Tunable laser (1), edge coupler (3), wavelength division multiplexer (4), optical antenna array (5) and off-chip aspheric lens (6); The tunable laser (1) is used to generate optical signals of different wavelengths. The optical signals are coupled into a waveguide via an edge coupler (3), and are transmitted into a wavelength division multiplexer (4) via the waveguide. The wavelength division multiplexer (4) sends the optical signals to the optical antennas corresponding to the optical antenna array (5) according to the wavelengths of the received optical signals. An off-chip aspheric lens (6) is provided above the optical antenna array (5). The off-chip aspheric lens (6) is used to collimate the optical beam and modulate the emission angle of the optical signal emitted by the optical antenna.

2. The wavelength-scanning high-power silicon nitride focal plane array laser radar transmitter according to claim 1, characterized in that: The optical antenna array (5) comprises n bus waveguides, each bus waveguide is connected to m arbitrary splitting ratio devices (7), and each arbitrary splitting ratio device (7) is connected to a grating coupler (8); the grating couplers (8) on the n bus waveguides are arranged correspondingly to form an antenna array with n rows and m columns.

3. The wavelength-scanning high-power silicon nitride focal plane array laser radar transmitter according to claim 1 or 2, characterized in that: It also comprises a driving circuit (2), wherein the driving circuit (2) is used to drive the tunable laser (1).

4. The wavelength-scanning high-power silicon nitride focal plane array laser radar transmitter according to claim 1, characterized in that: The wavelength division multiplexer (4) is implemented by using an arrayed waveguide grating or a cascaded multi-mode interferometer.

5. The wavelength-scanning high-power silicon nitride focal plane array laser radar transmitter according to claim 1, characterized in that: An optical antenna array (5) is used to couple the waveguide mode to the free space mode.

6. The wavelength-scanning high-power silicon nitride focal plane array laser radar transmitter according to claim 2, characterized in that: The splitting ratios of any splitting ratio device from the input end to the output end of the bus waveguide light are 1 / m, 1 / (m-1), 1 / (m-2)...1 respectively.

7. The wavelength-scanning high-power silicon nitride focal plane array laser radar transmitter according to claim 1, 2, 4 or 5, characterized in that: The edge coupler (3) is a wide wavelength edge coupler.

8. The wavelength-scanning high-power silicon nitride focal plane array laser radar transmitter according to claim 1, 2, 4 or 5, characterized in that: It also comprises a silicon nitride substrate, and the optical antenna array (5) is arranged on the upper surface of the silicon nitride substrate.

9. The wavelength-scanning high-power silicon nitride focal plane array laser radar transmitter according to claim 8, characterized in that: The edge coupler (3), the wavelength division multiplexer (4) and the optical antenna array (5) are an integrated structure, wherein the integrated structure is photoetched on a silicon nitride waveguide layer (030) of a silicon nitride substrate, wherein the silicon nitride substrate comprises, from bottom to top, a silicon base layer (010), a silicon dioxide buffer layer (020), a silicon nitride waveguide layer (030) and a silicon dioxide cladding layer (040).

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