Ultraviolet light-induced terahertz modulation of an indium oxide film

Active ultraviolet light-induced terahertz modulation of an indium oxide film is investigated. A large absorption modulation of ~66% is achieved upon illumination with a low intensity UV laser (11 mW/cm
²
). The interaction between indium oxide and a flexible metamaterial structure is investigated owing to the large UV-induced enhancement of photo carriers observed in an indium oxide film. We are able to realize absorption peak shifts of 37 GHz by changing the UV excitation light intensity. We also propose a multi-frequency switch by building a circular metallic split ring resonator whose gaps are filled with silicon, germanium, and indium oxide. In future, a photo-excited tunable multi-frequency metamaterial switch can be realized by irradiating the structure with multi-wavelength laser beam.