THz polarization-sensitive characterization of a large-area multilayer rhenium diselenide nanofilm

Recently, rhenium diselenide (ReSe₂) has attracted considerable attention due to its high anisotropy in the layer plane, which makes it a promising candidate for wide applications in electronics and optoelectronics. In this paper, we focus on the polarization-sensitive characteristics of a large-area multilayer ReSe₂ nanofilm in the terahertz (THz) region under passive and active conditions by means of THz time-domain spectroscopy. We demonstrate the passive ReSe₂ nanofilm with intrinsic THz polarization anisotropy. Maximum transmittance occurs only when the polarization direction of the incident THz wave is along the Re-chains direction. More importantly, THz polarization properties of the active ReSe₂ nanofilm by an external electric field applied in a selected directions are also demonstrated. The modulation depth of the THz transmission is up to 16% and the response time is on the order of picoseconds. In addition, a comparative experiment is performed on three kinds of THz polarizers, i.e., ReSe₂ nanofilm, carbon nanotubes (CNTs) and wire-gird, respectively. The results prove that the performance of the polarizer based on the active ReSe₂ nanofilm is comparable with those of CNTs and the THz wire-gird polarizer. Based on these studies, we believe that the polarization-sensitive ReSe₂ nanofilm can find important applications in ultrafast switches, filters and modulation devices in the THz region.