Dual-band bandpass filter based on compound metallic grating waveguide structure

In this paper, we proposed a novel dual-band bandpass filter based on subwavelength compound metallic grating deposited on the waveguide structure by using the finite-difference time domain (FDTD) method. The compound metallic grating is constructed by carving a groove on the top surface of every metal strip. The designed structure generates two remarkable transmission peaks with a dip in-between at normal incidence. Two transmission peaks with narrow bandwidth and high transmission depth is attributed to the existence of grooves in the designed structure. We research the implied physical mechanism of two resonance peaks and one dip by investigating the effect of different structure parameters on transmission spectrum and the electromagnetic field distributions at the location of resonance. It is found that the two resonance peaks are determined by different hybrid modes of F-P like resonance, waveguide resonance mode and SPP mode. Besides, angularly resolved spectra are presented to further reveal physical mechanism of two resonance peaks. This work can be used to develop a dual-band bandpass filter in the telecom wavelength range.