Research of ultra-narrow band filters based on silicon nitride subwavelength grating used in terahertz detection techniques

Abstract

As narrow-band pass filters are essential in terahertz(THz) applications, we present a ultra-narrow band filters based on silicon nitride subwavelength grating in this paper. Through rigorous coupled wave analysis, it can be seen that the main role of each structural factor or its influence on the spectral response characteristics are significantly different.Then, according to these laws, we get the design scheme by adjusting the structure factor of the subwavelength grating purposefully and pertinently. It can be seen from the results that the theoretical reflectance at 0.55 THz reaches 99.741%, and the half-peak frequency range is between −171MHz and +53 MHz. At the same time, the low sideband reflectance in the wide frequency band range of 0.2–0.8 THz indicates that the design can be used well for 0.55 THz signal in related THz detection technology.