Quad-band terahertz absorption enabled using a rectangle-shaped resonator cut with an air gap

Abstract

Quad-band terahertz absorption responses were theoretically investigated in a compact and simple design of a metamaterial absorber, which consisted of a rectangle-shaped metallic resonator with an air gap and an insulating medium layer on top of a metallic mirror. Herein, four resonance peaks with nearly unity absorption were achieved in this structure. The patterned structures on the layer couple strongly to the incident waves at four different resonance modes, leading to the quad-band absorption responses. For the design of the absorber, complex and accurate alignment of elements can be avoided compared to previous multimer structures. Moreover, we demonstrated a tunable terahertz absorber by introducing photosensitive silicon material in the gap of the top layer resonator. Results show that the number of resonance peaks can be controlled from quad-band to dual-band by varying the silicon conductivity. This demonstration can, therefore, provide a simple and effective strategy or method for the design of multiple-band and even tunable metamaterial absorbers.