Development Of Optical Phase Control Performance Test System For Optical Phased Array(OPA)

Compared with mechanical lidar,solid-state lidar can realize scanning steering without relying on mechanical structure,which reduces the wear and speed limit of mechanical structure,and is more conducive to integrated structure to reduce the size of component parts,thereby reducing the overall volume of the radar,It has the advantages of fast turning,durable,compact and light.At the same time,solid-state lidar also inherits the advantages of mechanical lidar.Laser detection should be used.Compared with traditional microwave radar,it has the advantages of small main lobe width,good coherence,concentrated main lobe energy,strong anti-interference ability,and fast response.In the solid-state lidar,the core component is the optical phased array(OPA).The commonly used materials for making the optical phased array are lithium niobate,liquid crystal,piezoelectric ceramics,etc.In recent years,the technology of optical phased array has developed rapidly.Optical waveguides quickly become a hot topic in the realization of OPA technology due to its easy-toimplement thermo-optical or electro-optical modulation and good compatibility with CMOS technology.However,there are still many problems to be solved in the application of silicon-based OPA in the actual industry.One is that it is limited to the current process level.In the process of etching the limit pitch waveguide,the final cost of the waveguide is often different from the design due to process errors.Rough edges,uneven waveguide spacing,etc.These small errors are amplified by the highly sensitive integrated optical circuit,resulting in amplitude errors and phase errors in a set of OPA waveguides.Therefore,each OPA chip needs to be tested for optical phase control performance before actual use to calibrate each steering The configuration of each waveguide control voltage or control current required by the angle to compensate for the influence of the amplitude error and phase error caused by the process on the formation of the far-field optical field by the beam scanning.This article has done the following work on this issue:First of all,this article introduces the close combat of OPA and solid-state lidar with OPA as the core at home and abroad,including one-dimensional scanning and two-dimensional scanning OPA,and briefly explains the bottleneck of the practical application of OPA industrialization today.Secondly,this paper analyzes the diffraction model of the one-dimensional OPA,introduces several main performance parameters for evaluating the quality of the far-field optical field,and further analyzes and simulates the influence of the waveguide spacing and the number of waveguides on the OPA far-field optical field grating lobes.,In order to further explain the choice of OPA waveguide spacingFurther,this article introduces the commonly used OPA beam scanning angle corresponding to the phase shift calibration common algorithms,mainly including the path-by-path search algorithm,hill climbing algorithm,simulated annealing algorithm,stochastic parallel gradient descent algorithm,genetic algorithm,etc.,through the description of the algorithm principle and The preliminary performance comparison introduces the advantages and disadvantages of each algorithm,and selectively simulates the performance of the algorithm through the far-field light field distribution model containing errors.Finally,the genetic algorithm has slow convergence and many far-field sidelobes.Attempt to put forward an improvement plan,and the simulation test shows that there is a certain performance improvement.Then,this article constructs a set of OPA chip's optical phase control performance test system on the OPA chip's fast optical phase control performance test.It mainly introduces the system's hardware composition,various interface protocols and software composition,and focuses on the program interface communication and The core algorithm code is explained.Finally,the performance of the entire system was tested,including the information communication test of the control computer to the various components of the system,and the calibration test of the OPA chip.Then,the system was used to test the scanning angle of the 64-channel equal-spacing OPA chip,achieving ±40 ° scan range and corresponding voltage calibration,the peak sidelobe level is less than 0.1,and during the test,the changes in the far-field light field distribution as the beam scan angle increases are observed and analyzed,and the problems encountered during the test Other issues,such as the thermal expansion of the chip and the thermal crosstalk between the waveguides,on the far-field optical field distribution are discussed.