Based on the tunable conductivity of silicon as a function of incident pump power, a photoexcited switchable dual-function metamaterial absorber for sensing and wideband absorption at the THz band is designed in this paper. The absorber has an absorption peak at 2.08 THz with the absorption up to 99.6% when the conductivity of silicon is 150 Sm-1, which can be used for sensing. The refractive index sensitivity of the absorption peak is up to 456 GHz/RIU. A wideband absorption is generated from 3.4 THz to 4.5 THz with the bandwidth of 1.1 THz as the conductivity σsi = 12,000 Sm-1. The generation mechanism of the sensing absorption peak and wideband absorption is explained by monitoring the surface current, electric, and magnetic field distribution at some absorption frequencies. It has the advantages of being simple and having a high sensitivity, and wideband absorption with wide application prospects on terahertz communication, electromagnetic stealth, and biochemical detection.
Keywords: THz band; metamaterial absorber; sensing; wideband absorption.