Elimination of the zeroth order for four-port power separation by T-ridge metamaterial

Abstract

Abstract In this paper, we describe a transmissive grating that eliminates the zeroth order, based on a T-ridged grating structure. The transmission efficiency of the zeroth order under transverse-electric polarization is 0.19%, and the diffraction efficiencies are 22.17% and 21.77% for the ±first and ±second orders, respectively. The transmission efficiency of the zeroth order under transverse-magnetic polarization is 0.11%, and the diffraction efficiencies are 24.12% and 21.93% for the ±first and ±second orders, respectively. In addition, a normalized electric-field diagram is obtained using a finite-element method and the physical mechanism inside the grating is comprehensively analyzed. The diffraction efficiency of each order is calculated for fluctuating values of the wavelength, period and duty cycle and optimized grating parameters. It is concluded that the grating has good tolerance and stability. The analytical results show that the T-ridged four-port grating has good development prospects in the laser field.