Wide spectral range guided-mode resonant grating designed for the wet etching process

We present wideband guided-mode resonant (GMR) gratings made of Si on a SiO2 substrate. Based on the base angle of the grating as the crystal orientation angle (54.74°) of Si, the design process of reflectors suitable for TM-polarized waves is demonstrated in the near-infrared (NIR) and mid-infrared (MIR) wavelengths. Benefiting from the mutual attraction and interaction of the two GMR modes, the bandwidth of reflectivity above 99% for the reflector under the NIR and MIR bands reaches 297 nm (from 1416 nm to 1713 nm) and 657 nm (from 3154 nm to 3811 nm), respectively. In addition, the effects of the incident light source state and the structural parameters on the performance of the reflector are analyzed in detail. The results show that the reflector will maintain good tolerance and stability during fabrication and use. This work will be compatible with the wet etching process in the microelectromechanical system, and the results can be extended to the design of broadband GMR reflectors in other wavelength bands.