Numerical analysis of a dual-wave band guided-mode resonance filter with embedded bilayer asymmetric metallic gratings

Abstract

In this paper, a novel guided-mode resonances (GMRs) based embedded dual-wavelength filter, which had the bilayer gratings located at the two sides of dielectric substrate and arranged at asymmetric position, was investigated and studied theoretically. As compared to symmetric structures that usually provided single wavelength of transmission resonance, as one normal incidence was used for transverse magnetic polarized light, the designed asymmetric structure could generate two remarkable narrow band wavelengths of transmission resonance. The parameters to affect the resonance wavelengths and the transmission resonance Q value (Q = λ/Δλ) of two bands were the distance between the two metallic gratings, the relatively lateral positions of the upper and lower gratings, the number of structure period, the thicknesses of metallic gratings, and the thickness of dielectric film. By optimizing the designed parameters, a GMR device with two resonance wavelengths located at 1239 and 1302 nm showed relative optimal performance because they had high transmission depth (99.9% and 90%) and ultra-narrow transmission bandwidth (2.8 and 1.8 nm) at the two resonance wavelengths. The presented structure can offer a potential route towards dual-band narrow-band filters and refractive index sensors in the near infrared.