November

Bild des Monats November 2022

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.

Dieses Bild wurde eingereicht von Dr. Arash Rahimi-Iman (in Kooperation mit Gen Liu und Weien Lai).

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