Tri-channel independent switching terahertz filter based on metal-graphene hybrid coding metasurface

Abstract

Terahertz (THz) filters are the core devices for practical application in THz communication technology. Recently, design of multi-channel filters with high modulation rates remains to be a challenge. In this paper, a three channels switchable THz filter based on metal-graphene hybrid metasurface is proposed. The unit cell is consisted of "n"-shaped and "u"-shaped split-ring resonators (SRRs) with different sizes, and the graphene bar is embedded at the gap of two SRRs. The four bandpass modes with single transparency windows, double two transparency windows, and three transparency windows can be freely switched by applying voltage to the left/right electrodes of the filters. Its central frequencies of transparency windows are located at 0.80 THz with modulation depth up to 49%, 1.14 THz (constant transparency windows), and 1.58 THz with modulation depth up to 68%, respectively. In addition, an equivalent circuit model is proposed to demonstrate the control mechanism. This research result not only provides a new method for the design of reconfigurable multifunctional THz modulation devices, but also give theoretical model to promote the development of multi-channel filter technology in THz communication technology.