Structure design of two-dimensional multilayer subwavelength grating based on ant colony algorithm

two-dimensional polarization-independent subwavelength grating structure suitable for long wave infrared band have been proposed. Symmetric two-dimensional structure is used to eliminate polarization dependence of one-di-mensional grating and increase luminous flux. The evaluation function of grating optimization was proposed,and then the optimization of grating structure parameters was transformed into a path optimization problem. Finally,the ant colo-ny algorithm was used to solve the optimal grating structure parameters. Simulation results show that the proposed two-dimensional multilayer structure has the advantages of polarization independence,narrow grating period,narrow spec-tral bandwidth and low side band in 10 similar to 13 mu m band. The convergence speed of the proposed optimization design meth-od is fast. The transmittance of the polarization direction of transverse electric (TE) and transverse magnetic(TM) reaches 70%,and the spectral bandwidth is 260 nm.