Omnidirectional Light-Tunable Broadband Terahertz-Wave Hybrid Antireflection Coating Composed of PEDOT:PSS and Graphene on Silicon
The demonstration of an actively configurable broadband terahertz (THz) antireflection (AR) coating supports the achievement of high-performance and versatile THz components. Here, we explore an AR coating based on an impedance matching method employing a composite film structure made of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) on graphene placed on a silicon substrate which can be driven by near-infrared light. Omnidirectional broadband properties of such active AR coating can be efficiently achieved by charge-carrier-density-tunability via optical irradiance of less than 0.27 W·cm–2, with which suppression of THz-wave reflection is demonstrated for incidence angles from 0 to 70°, concerning the broadband frequency range of 0.1–3.0 THz. In addition, the composite film features an ultrafast response time of ∼5 ps. Furthermore, our recent joint study within the Sino-German FNMS-COOP group’s frame, involving scientists from Hefei, Hangzhou and Gießen, shows that the active AR coating can improve the performance of a reflectance-tunable THz-wave polarization reflector by the elimination of Fabry–Pérot interference (https://doi.org/10.1021/acsami.2c10186). By investigating the NIR-irradiance dependence of the hybrid system’s active AR mechanism, the essential role of the PEDOT:PSS/graphene layers in promoting the charge separation at the interface and therefore changing the photoconductivity of the composite film to achieve impedance matching under optical excitation is highlighted.
