Metal Mesh Metasurfaces as Dual-Band Bandpass Filters for Terahertz Frequencies

In this paper, we propose a new design strategy for metal mesh filters (MMFs) based on the analysis of the spatial symmetry of bound states in the continuum (BICs), and manipulation and control of their characteristics using resonances that originate from the BICs when the structure of MMF is spatially perturbed. The design of a dual-band polarization-insensitive terahertz bandpass filter with wide upper stopband characteristics using a single conducting layer patterned with rectangular holes is presented. The transmission response of the MMF with two poles is obtained to realize dual-band characteristics and three zeros to suppress the stopband. The proposed design has achieved broadband transmission characteristics for both TE and TM polarizations, with center frequencies at 0.516THz and 0.734THz, 3dB bandwidths of 25% and 17%, respectively, and upper stopband from 0.887THz to 1.6THz with over 10dB suppression.