Wide-angle scanning optical phased array and laser radar

Abstract

The invention particularly relates to a wide-angle scanning optical phased array and a laser radar. The optical phased array comprises a laser, a beam splitting network, an optical amplifier array, a phase shifter array and an antenna array which are arranged in sequence. The antenna array comprises a plurality of groups of waveguide antennas which are arranged side by side; any waveguide antenna comprises a main channel waveguide and photonic crystal gratings arranged on the two sides of the main channel waveguide. Evanescent coupling is formed through the main channel waveguide and the photonic crystal gratings on the two sides of the main channel waveguide, so that an optical signal is coupled to the photonic crystal gratings on the two sides under the action of the evanescent coupling after being transmitted through the main channel waveguide, and then is diffracted to a free space through the photonic crystal gratings to form light beam scanning. Meanwhile, the light beam diffracted to the free space is transmitted by the slow wave of the photonic crystal in the photonic crystal grating, so that the longitudinal scanning angle of the optical phased array provided by the invention is doubled.

Description

Technical Field

[0001] The present invention relates to the field of optical communication technology, and in particular to an optical phased array and a laser radar for wide-angle scanning. Background Art

[0002] A phased array is an array of phase-controlled elements. It achieves beam steering by adjusting the phase of the outgoing wave of each element. Compared with traditional mechanically controlled beam steering technology, it has a faster response speed and greatly improves pointing accuracy and stability. Optical phased arrays operate in the optical frequency band and can be used for point-to-point free-space optical communications, optical detection and measurement, holographic imaging, and the generation of vortex light.

[0003] In the field of laser radar, two-dimensional scanning of lasers can be achieved through phased array technology. However, due to the composition structure of the phased array, it is difficult to achieve a wide range of scanning angles, which limits the scanning range of the phased array-based laser radar and limits the application scenarios of the laser radar. Summary of the invention

[0004] In order to solve the technical problem that the scanning range of laser radars using phased array technology in the prior art is limited, a wide-angle scanning optical phased array and laser radar are provided, which have at least the advantages of wide scanning angle and small size.

[0005] First aspect

[0006] The present invention provides an optical phased array for wide-angle scanning, comprising:

[0007] A laser, a beam splitting network, an optical amplifier array, a phase shifter array and an antenna array are arranged in sequence;

[0008] The antenna array includes multiple groups of waveguide antennas;

[0009] Any of the waveguide antennas described above comprises a main channel waveguide and a photonic crystal grating arranged on both sides of the main channel waveguide.

[0010] Furthermore, the photonic crystal grating includes a silicon strip and photonic crystals arranged on the silicon strip and distributed in an array;

[0011] Adjacent photonic crystals are distributed non-uniformly.

[0012] Furthermore, a coupling gap is provided between the silicon strip and the main channel waveguide;

[0013] The coupling gap is 220nm-250nm.

[0014] Optionally, the radius of the photonic crystal is 75nm-100nm; the lattice constant of the photonic crystal is 450nm-500nm.

[0015] Furthermore, the laser comprises at least two groups of broadband tunable lasers connected in series.

[0016] Furthermore, the beam splitting network includes a multi-stage Y-type beam splitter, a multi-mode interference beam splitter or a star-coupled beam splitter.

[0017] Optionally, the optical amplifier array is arranged in each branch of the beam splitting network.

[0018] Optionally, the phase shifter array includes a silicon-based electro-optical phase shifter, a thermo-optical phase shifter or a III-V MOS phase shifter.

[0019] Optionally, the laser, beam splitting network, optical amplifier array, phase shifter array and antenna array are all made of III-V Group materials and are heterogeneously integrated into a single chip.

[0020] Second aspect

[0021] The present invention provides a laser radar, comprising an optical phased array for wide-angle scanning as provided in any embodiment of the first aspect.

[0022] In summary, the present invention provides a wide-angle scanning optical phased array and laser radar having at least the following advantages:

[0023] 1. One of the main concepts of the present invention is to form evanescent coupling through the main channel waveguide and the photonic crystal gratings on both sides thereof, so that after the optical signal is transmitted through the main channel waveguide, it is coupled to the photonic crystal gratings on both sides under the action of evanescent coupling, and then diffracted into the free space through the photonic crystal grating to form a beam scan. At the same time, the light beam diffracted into the free space is transmitted by the slow wave of the photonic crystal in the photonic crystal grating, which doubles the longitudinal scanning angle of the optical phased array provided by the present invention, thereby enabling the present invention to have the advantage of wide-angle scanning;

[0024] 2. Another main concept of the present invention is to design the arrangement of the waveguide antenna based on photonic crystal so that it presents a non-uniform distribution, thereby overcoming the technical problem of limited lateral field of view caused by excessive center spacing when the waveguide antenna based on photonic crystal is evenly arranged, so that it can provide a larger lateral field of view while achieving a larger array area;

[0025] 3. Another main concept of the present invention is to design the radius and lattice constant of the photonic crystal so that it can achieve the slow light effect within the target wavelength, thereby improving the dispersion of light and further enhancing the scanning sensitivity of the antenna array;

[0026] 4. One of the main concepts of the present invention is to design the structure of the laser in series, so that the longitudinal scanning angle of the optical phased array provided by the present invention is doubled, thereby making the scanning width of the phased array provided by the present invention larger;

[0027] 5. Based on the above technical concept, the present invention further provides a laser radar on the basis of the optical phased array, so that when the laser radar uses the phased array for two-dimensional scanning, the longitudinal angle of the scan is doubled and the lateral angle reaches ±60°, thereby making the laser radar provided by the present invention have broader application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention will be further described in detail below in conjunction with the accompanying drawings and preferred embodiments, but those skilled in the art will appreciate that these drawings are drawn only for the purpose of explaining the preferred embodiments and therefore should not be used as a limitation on the scope of the present invention. In addition, unless otherwise specified, the drawings are only schematically representing the composition or structure of the described objects and may contain exaggerated displays, and the drawings are not necessarily drawn to scale.

[0029] Figure 1 A schematic diagram of the structure of an optical phased array for wide-angle scanning provided by an embodiment of the present invention;

[0030] Figure 2 A schematic structural diagram of a photonic crystal waveguide antenna provided by an embodiment of the present invention;

[0031] Figure 3 A schematic diagram of sensitivity comparison of a photonic crystal grating provided by an embodiment of the present invention;

[0032] Figure 4 A schematic diagram comparing the radius and lattice constant of a photonic crystal provided by an embodiment of the present invention;

[0033] Figure 5 A schematic diagram comparing the far-field intensity distribution at 0° and 60° lateral scanning angles provided by an embodiment of the present invention;

[0034] Figure 6 A schematic diagram of attenuation loss of a coupling gap provided by an embodiment of the present invention;

[0035] 1. Laser; 2. Beam splitting network; 3. Optical amplifier array; 4. Phase shifter array; 5. Antenna array; 6. Substrate; 51. Waveguide antenna; 511. Main channel waveguide; 512. Photonic crystal grating; 513. Coupling gap; 512a. Silicon strip; 512b. Photonic crystal. DETAILED DESCRIPTION

[0036] The following is combined with Figures 1 to 6, the present invention is described in detail.

[0037] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0038] The main technical concept of the present invention is to expand the scanning range of the optical phased array through the structural design of the laser 1 and the antenna array 5 on the basis of the existing optical phased array, thereby improving its application prospects in the field of laser radar.

[0039] See also Figure 1 FIG. 1 is a schematic diagram of the structure of an optical phased array for wide-angle scanning provided by an embodiment of the present invention.

[0040] Specifically, the optical phased array provided by the present invention includes a laser 1, a beam splitting network 2, an optical amplifier array 3, a phase shifter array 4 and an antenna array 5 which are arranged in sequence. The laser 1 can adopt different micro-ring radii to correspond to different ranges of laser resonance wavelength ranges, thereby covering different bands. The beam splitting network 2 is used to split the resonant laser generated by the laser 1, and amplify the resonant laser in the beam splitting network 2 through the optical amplifier array 3, so that the resonant laser is adjusted under the action of the phase shifter array 4, thereby realizing the power amplification of the scanning laser finally emitted through the antenna array 5.

[0041] For further information, see Figure 2 FIG. 5 is a schematic structural diagram of a photonic crystal 512b waveguide antenna 51 provided in one embodiment of the present invention.

[0042] The antenna array 5 provided by the present invention includes a plurality of groups of waveguide antennas 51 arranged in parallel, and any waveguide antenna 51 includes a main channel waveguide 511 and a photonic crystal grating 512 arranged on both sides of the main channel waveguide 511. The main channel waveguide 511 and the photonic crystal grating 512 are both arranged on the substrate 6. At the same time, a coupling gap 513 is reserved between the main channel waveguide 511 and the photonic crystal grating 512. The main channel waveguide 511 and the photonic crystal grating 512 can be separated by setting the coupling gap 513, so that the diffracted light in the photonic crystal grating 512 does not affect the transmission of the signal light in the main channel waveguide 511, and the adjustment of the coupling gap can adjust the coupling strength of the light, so that waveguide antennas 51 of different lengths can be prepared.

[0043] In addition, the photonic crystal grating 512 includes a silicon strip 512a and a plurality of photonic crystals 512b etched on the silicon strip 512a. Since the parameters of the photonic crystals 512b are set in the photonic bandgap, slow light transmission can be achieved, thereby achieving the purpose of increasing the longitudinal angle.

[0044] Furthermore, the photonic crystal 512b in the photonic crystal grating 512 adopts a non-uniform sparse array, which overcomes the problem of limited lateral field of view caused by the large center spacing when the uniform array is arranged, and can simultaneously achieve a larger array area and a larger lateral field of view. The far-field intensity distribution of the non-uniformly distributed waveguide antenna 51 array based on the photonic crystal 512b can reach a horizontal field of view of ±60°, and a 128-channel array can fill a lateral aperture of 1mm width. A larger array area can produce a smaller divergence angle.

[0045] It is worth explaining that the array composed of the non-uniformly distributed waveguide antennas 51 based on photonic crystals 512 b can be obtained by a particle swarm algorithm, a genetic algorithm or other optimization algorithms.

[0046] Optionally, taking a genetic algorithm as an example, the element position of a non-uniform array is defined as an optimization variable, a population is randomly generated, each individual represents a possible array layout, and the sidelobe suppression ratio is used as a fitness function. Through selection, crossover, mutation, replacement, optimization and other algorithm processes, it is iterated to finally obtain an optimized result (array coordinate group).

[0047] Furthermore, the divergence angle of the phased array is inversely proportional to the effective aperture area of ​​the non-uniform array.

[0048] Optionally, the laser 1 can be connected in series in the main channel silicon waveguide through two or more groups of laser components, and output optical signals of different wavelength ranges respectively. Since the longitudinal scanning angle range of the optical phased array is controlled by the wavelength range, increasing the number of lasers 1 can directly double the longitudinal scanning angle. Each laser component can be controlled independently.

[0049] For further information, see Figure 3 FIG. 5 is a schematic diagram showing a sensitivity comparison of a photonic crystal grating 512 provided in accordance with an embodiment of the present invention.

[0050] Specifically, the present invention utilizes the slow light effect to increase the longitudinal scanning range to more than 30° (typical value 15° / 100nm) within the wavelength range of 1500-1600nm.

[0051] For further information, see Figure 4 FIG. 1 is a schematic diagram showing a comparison of the radius and lattice constant of a photonic crystal 512 b provided in an embodiment of the present invention.

[0052] Specifically, the lattice constant of the photonic crystal 512 b is 480 nm, and the energy band diagram of the photonic crystal 512 b when the radius is 95 nm has a photonic bandgap covering a wavelength range of 1500-1600 nm.

[0053] Optionally, when the lattice constant of the photonic crystal 512b increases, the diffraction angle of the waveguide antenna 51 deflects toward the positive direction, so that the lattice constant of the photonic crystal 512b can be determined based on the light output angle of the waveguide antenna 51, and thus can be applied to the needs of optical phased arrays with different light output angles.

[0054] For further information, see Figure 5 FIG. 1 is a schematic diagram showing the comparison of far-field intensity distribution at lateral scanning angles of 0° and 60° provided by an embodiment of the present invention.

[0055] Specifically, when the photonic crystal 512b array adopts a non-uniform sparse distribution, the lateral scanning angle can reach ±60°.

[0056] For further information, see Figure 6 FIG. 4 is a schematic diagram of the attenuation loss of a coupling gap provided by an embodiment of the present invention.

[0057] Specifically, the coupling gap 513 is 220nm-250nm.

[0058] Optionally, when the width of the main channel waveguide 511 is 500 nm, the width of the silicon strip 512a is 300 nm, the lattice constant of the photonic crystal 512b is 480 nm, and the radius is 95 nm, Figure 6 The wavelength of the waveguide antenna 51 shown in (a) is 1550 nm.

[0059] Optionally, when the coupling gap 513 is 240nm, the attenuation loss of the waveguide antenna 51 in the 1500nm-1600nm band is 2dB / mm, and thus the setting of the coupling gap 513 can effectively regulate the coupling strength, thereby controlling the attenuation loss of the waveguide antenna 51 and improving the signal transmission quality of the antenna array 5.

[0060] The present invention is described in detail above. The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the present invention and its core ideas. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present invention, the present invention can also be improved and modified in a number of ways, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. An optical phased array for wide-angle scanning, characterized in that: include: A laser (1), a beam splitting network (2), an optical amplifier array (3), a phase shifter array (4) and an antenna array (5) are arranged in sequence; The antenna array (5) comprises a plurality of groups of waveguide antennas (51) arranged side by side; Any of the waveguide antennas (51) comprises a main channel waveguide (511) and a photonic crystal grating (512) arranged on both sides of the main channel waveguide (511).

2. The wide-angle scanning optical phased array according to claim 1, characterized in that: A coupling gap (513) is provided between the photonic crystal grating (512) and the main channel waveguide (511); The coupling gap is 220nm-255nm.

3. The wide-angle scanning optical phased array according to claim 1, characterized in that: The photonic crystal grating (512) comprises a silicon strip (512a) and photonic crystals (512b) arranged on the silicon strip (512a) and distributed in an array; Adjacent waveguide antennas (51) are distributed non-uniformly.

4. The wide-angle scanning optical phased array according to claim 3, characterized in that: The radius of the photonic crystal (512b) is 75nm-100nm; the lattice constant of the photonic crystal (512b) is 450nm-500nm.

5. The wide-angle scanning optical phased array according to any one of claims 1 to 4, characterized in that: The laser (1) comprises at least two groups of broadband tunable lasers connected in series.

6. The wide-angle scanning optical phased array according to claim 5, characterized in that: The beam splitting network (2) comprises a multi-stage Y-type beam splitter, a multi-mode interference beam splitter or a star-type coupling beam splitter.

7. The wide-angle scanning optical phased array according to claim 5, characterized in that: The optical amplifier array (3) is arranged in each branch of the beam splitting network (2).

8. The wide-angle scanning optical phased array according to claim 5, characterized in that: The phase shifter array (4) comprises a silicon-based electro-optical phase shifter, a thermo-optical phase shifter or a III-V MOS phase shifter.

9. The wide-angle scanning optical phased array according to claim 1, characterized in that: The laser (1), beam splitting network (2), optical amplifier array (3), phase shifter array (4) and antenna array (5) are all made of III-V group materials and are heterogeneously integrated into a single chip.

10. A laser radar, characterized in that: It comprises an optical phased array for wide-angle scanning as described in any one of claims 1 to 9.

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