Optimal Design Of Optoelectronic Integrated Optical Phased Array

The laser source has the characteristics of concentrated energy,small divergence angle and good coherence.It is often used for sensing detection of the environment.The mechanical structure of the lidar technology is mature,but the volume is large and the cost is high.The size of the device can be reduced by using a lidar consisting of phased array structure.Lithium niobite,liquid crystal and piezoelectric ceramics are commonly used to fabricate phased array lidars.The phased array made of lithium niobate has high precision,but it has high operating voltage,high power consumption and small scanning angle.The phased array fabricated by liquid crystal needs low driving voltage,has low power consumption,long service life and large scanning angle,but the response speed is slow,the thermal stability is poor,and the operating wavelength is limited.The phased array made of piezoelectric ceramics has wide transmission spectrum,low loss and low price,but with the high working voltage and cost.With the development of silicon-based optoelectronic technology,a large number of optoelectronic devices can be integrated on a single chip.Optical phased arrays fabricated by silicon-based Optoelectronics Technology have the characteristics of small size and low cost.However,there are many difficulties in fabricating optical phased arrays using silicon-based optoelectronic technology.In this paper,optical phased array structure is analyzed and designed,mainly in the following aspects:Firstly,the research progress of silicon-based optoelectronic integrated optical phased array is introduced,including one-dimensional scanning optical phased arrays and two-dimensional scanning optical phased arrays.The bottlenecks in the application of optical phased arrays are briefly introduced.Secondly,the array model of optical phased array is analyzed,and the main performance parameters of far-field beam are introduced.The influence of waveguide number and waveguide spacing on the far-field beam of equal-spacing optical phased array are analyzed and discussed.The reasons for the grating lobes generated by the equi-spaced optical phased array far-field beams are analyzed.The suppression effect of non-equal-spacing layout on grating lobes is briefly summarized.Then,the commonly used algorithms for designing non-equidistant optical phased arrays are introduced,including genetic algorithm and particle swarm optimization algorithm.The common feature of these algorithms is that they need repeated iteration when used to design the non-equidistant optical phased array.To solve this problem,this paper carries out some optimizations and proposes a pattern search algorithm,which can design non-equidistant optical phased arrays with high performance without repeated iteration.The far-field beam and the scanning effect of a non-equidistant optical phased array designed by this algorithm are demonstrated.Compared with the reported design scheme,the demonstrative design scheme can achieve a larger scanning range and a smaller beam angle with fewer number of waveguides.Finally,it is difficult to ensure the uniformity of waveguides in the process of unequal spacing fabrication,and the spacing of waveguides can meet the design requirements.In this case,the far-field diffraction beam will deviate from expectation.The influence of phase error and amplitude error on far-field diffraction beam is analyzed.Based on a non-equidistant optical phased array model,the influence of random phase error and amplitude error on the main performance index of far-field beam is predicted by using Chebyshev inequality.The theoretical prediction results are in good agreement with the simulation results using MATLAB.In this paper,the general expression of peak sidelobe level range in the presence of phase and amplitude errors is obtained,which can effectively improve the efficiency of the beam calibration and provide useful reference for engineering practice.