Tunable thermal mid-IR conducting polymer antenna arrays

While initial studies on conducting polymer plasmonic antennas have focused on the near-infrared spectral range, their reversible plasmonic-dielectric switchability presents significant potential also for the mid-infrared (mid-IR) around 10 mm which is relevant for the control of thermal emission at room temperature.  Here, we extend the applicability of conducting polymers to tunable thermal mid-IR applications. We demonstrate scalable fabrication of poly(3,4-ethylenedioxythiophene:tosylate) (PEDOT:Tos) microantenna arrays through photolithography and provide systematic size and shape investigation using electron-beam lithography. The polymeric microantenna arrays show clear asymmetric Fano-type mid-IR resonances which are spectrally tunable in the thermal range from 6 mm to 12 mm via the size, periodicity and shape of the antennas. The optical response of the antenna arrays could be reversibly switched ‘OFF’ and ‘ON’ by tuning the polaronic charge carrier concentration in the antennas via the polymer’s redox state. The results open new routes to dynamically control mid-IR thermal emission, with potential applications including beam steering, adaptive camouflage and tunable radiative cooling.