Calculation Of Reflection Characteristics Of One Dimensional Composite Grating

The diffraction and reflection characteristics of micro-nano optical structures have been studied in many fields such as grating fiber vibration sensing technology,comprehensive utilization of solar energy and solar battery.However,the diffraction and reflection characteristics in the micro-nano optical structure are usually selectivity of wavelength,grating period,grating slot depth and incident Angle,which puts forward many higher technical requirements to adjust the diffraction and reflection characteristics of the spectrum and direction of the object in the micro-nano optical structure.Among all the micro/nano optical structures,one dimensional grating has been widely used because of its simple structure,convenient processing and good parameter adjustment effect.The simple grating instrument has the advantage of relatively narrow modulation bandwidth,so it is not suitable to modulate the absorption ratio of the whole spectrum.Therefore,this paper proposes a one dimensional composite grating formed by the combination of two simple gratings with different duty cycles.Based on the theory of strict coupled wave analysis method,this paper briefly introduces the theory of strict coupled wave analysis method,and then analyzes the modeling of one-dimensional simple periodic structure gold grating and one-dimensional composite gold grating structure.According to the Maxwell equations,the Maxwell equations were expanded by Fourier transform,and then the reflection efficiency of the one-dimensional gold grating with simple periodic structure and the one-dimensional composite gold grating with different parameters were obtained by Matlab programming.The reflection efficiency of TE,TM polarization and conical incident are analyzed under different incident Angle,wavelength,grating period,grating slot depth and Fourier order.The influence of different parameters on the reflectivity of one-dimensional composite grating and onedimensional simple grating under different duty ratios is analyzed.The program solves the convergence problem of the transmission matrix.The numerical simulation shows that the convergence of the scattering matrix is better.The research results of this paper have certain theoretical derivation reference and practical application reference value for the design of onedimensional composite grating materials and the analysis of reflection characteristics.At the same time,the application of RCWA in aperiodic grating is studied,and the PML condition is added by the coordinate analytic continuation method,and the supercell method is used to carry out the research.