Shape analysis of wavelength-insensitive grating in the resonance domain

A triangular grating was compared with a rectangular one to investigate the effect of the shape, polarization and wavelength on the transmissivity and the diffraction angle distribution. The rigorous coupled-wave analysis (RCWA) and the nonstandard finite-difference time-domain (NS-FDTD) algorithm were used for the calculation. We found that the triangular grating in TE mode had the least wavelength dependence in the resonance domain, and this was explained by two independent parameters—(depth/wavelength) and (diffraction order × wavelength / period), whose ratio of the contribution to the diffraction efficiency equation was dependent on grating shape and polarization.

Research highlights
► We calculated gratings for different shape and polarization in the resonance domain.
► RCWA and NS-FDTD were used as the calculation method.
► The triangular grating in TE mode had the least wavelength dependence.
► This was explained by two independent parameters.
► The parameters are (depth/wavelength) and (diffraction order × wavelength / period).