Optimization And Simulation Of Dammann Gratings Based On Micro G-A Algorithm

Laser is practically used in many fields in the rapidly advancing 21st century.With the precision of experiments or manufacture processing increases,more accurate quality parameters of the emission field spot are also increasingly required.Compared with traditional spectroscopes,the diffraction spectroscope is widely used with advantages of high accuracy and low weight.Taking Dammann grating as an example in this paper,the vector diffraction calculation method is more suitable for sub-wavelength Dammann grating and the optimization iteration method is used to continuously optimize its structural parameters.This not only improves the quality parameters of Dammann grating,but also simplifies the experimental structure.Mirco G-A algorithm is the core optimization algorithm used in this paper.As the pseudo-global optimization mechanism of Mirco G-A algorithm can greatly reduce computational complexity while maintaining the accuracy,it is used to optimize the Dammann grating in this paper.The main work of this paper is as follows1、Quality parameter analysis of two kinds of errors caused by experiments.The first kind is the error caused by the inadequate etching accuracy.With the etching width increases to 10%of the total width,the difference percentage of T 0 level diffraction efficiency is as high as 286.70220%.The second kind is the error caused by the deviation of the incident light from the normal direction.With the left-right angle deviation increase to±10°,the difference percentage of T 0 level diffraction efficiency can be as high as 286.70224%2、Three types of sub-wavelength Dammann gratings are optimized and simulated,including 1×9 one-dimensional Dammann grating,1×8 one-dimensional Dammann grating and 3×3 two-dimensional Dammann grating.They are quantified respectively for the quality parameters(diffraction efficiency and inhomogeneity rate),grating structure parameters(single periodic width,etching depth,catastrophe coordinate value)and the distribution of emitted light field(diffraction efficiency at all levels,angular spacing of spot,single periodical distribution of EY component).The result shows that the diffraction efficiency of 1×9 grating is higher than 86%and the inhomogeneity rate is about 11%.The diffraction efficiency of 1×8 grating is higher than 83%(not including zeroth-order efficiency)and the inhomogeneity rate is about 2.8%.The diffraction efficiency of 3×3 two-dimensional grating is higher than 70%and the inhomogeneity rate is about 1%.The research result is of guiding significance for experiments and processing in future.