The Vector Design And Optimization Of Beam Splitter With Wide Diffraction Angle

As a tool manipulating light based on diffraction theory,diffractive optical elements become increasingly accepted in electronic devices.Beam splitter is a typical example for this trend since it plays an important role in realizing the facial recognition based on 3D structured light.To broaden the range of perception,wider diffraction angle is needed for beam splitters,which leads to finer structures whose performance only vector simulation can correctly simulate.A better perception performance requires the energy distribution to be uniform,which needs optimization algorithms.Only if combine vector simulation and optimization algorithm can the beam splitters with large diffraction angle be successfully designed.Compared with scalar approximation,vector simulation consumes far more computation power,which leads to unacceptable computation consumption and consequent low optimization efficiency if an improper algorithm is chosen.To achieve efficient design,this paper is organized as follow:1.The vector iterative Fourier transform algorithm,whose optimization process is performed on the basis of scalar results,is proposed.This algorithm is used for the design of forty 5×5 beam splitters with a maximal diffraction angle of 35°,beam splitters with cross-shaped and X-shaped diffraction patterns,respectively.The proposed algorithm reduces computation consumption by about 200 times compared to the combination of genetic algorithm and vector simulation when beam splitters with the same parameters are designed.Compared with the design methods without the basis of scalar results,the proposed method has the ability to screen the initial solutions.2.To solve the problem that the(0,0)order is hard to be suppressed,the scalar solution with a suppressed amplitude coefficient of(0,0)order is compensated during the vector optimization,which proved to be effective in designing the 7×7 beam splitter with a maximal diffraction angle of 70°,whose uniformity error improves from 0.4701 to 0.2622.Compared with other similar works about beam splitters with large diffraction angle in two-dimensional space,the proposed method only consumes about their 30%-80% computational power.Finally,the machining error is simulated to analyze its influence in actual fabrication.