Subwavelength grating wideband reflectors with tapered sidewall profile

One main difference between practical device and ideal design for subwavelength grating structure is the tapered sidewall profile of grating, which is normally obtained by the practical CMOS-compatible fabrication and etching process. Our work has investigated the impacts of tapered sidewall profile on the subwavelength grating wideband reflector characteristics. Both zero-contrast gratings (ZCG) and high-contrast gratings (HCG) are numerically investigated in detail and the results show a distinct differences of the impacts of tapered sidewall profile of grating. The simulation results reveal that this factor play a critical role in determining the reflection bandwidth, average reflectance, and the band edge. Our study has potential in guiding the utilization of subwavelength grating wideband reflector on application of a variety of nanophotonic devices and their integration, as well as to facilitate the design of the fabrication process on the control of tapered sidewall profile.