Antireflection Coatings Based on PEDOT:PSS Conductive Polymer Using d-Sorbitol Additives for Terahertz Spectroscopy and Imaging

Optical antireflection has been employed for a variety of applications in terahertz spectroscopy and detectors. However, current methods encounter challenges in terms of cost, bandwidth, structural complexity, and performance. In this study, a low-cost, broadband, and easily processed THz antireflection coating scheme based on the model of impedance-matching effect is proposed, using a 6 wt % d-sorbitol-doped poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (s-PEDOT:PSS) film. By adjusting the thickness of the s-PEDOT:PSS film, these biocompatible conductive polymers enable a significant reduction of Fresnel reflection and operate over a broad bandwidth between 0.2 and 2.2 THz. Applying the antireflective coating to the surface of the sample substrate and electro-optic probe crystal in THz spectroscopy and near-field imaging shows that the spectral resolution is significantly improved, and the devices exhibit more excellent intended performance. The findings of this study could aid in improving the measurement capability of various THz time-domain spectroscopy and imaging system.