Multifunctional terahertz devices hold great promise for terahertz (THz) optical systems. Here, we present an ultrathin, highly flexible and optically transparent terahertz polarizer based on tin-doped indium oxide (ITO) and flexible conformal films of polyethylene terephthalate. The flexible optical transparent polarizer (FOTP) was theoretically investigated and experimentally characterized by UV–vis spectrophotometry and THz time-domain system. In the FOTP, THz conductivity of ITO films is mainly dominated by DC conductivity. The FOTP reveals a high optical transmittance of more than 60% in the visible region, a high extinction ratio of about 20 dB in the 0.1 THz–2.5 THz and a low insertion loss below 2 dB in the 0.1 THz–1.4 THz. The proposed FOTP can significantly improve the overall performance of THz optical systems and be easily fabricated by commercial display techniques. Our concept opens up a new window for highly flexible and optically transparent THz devices.

The research on novel terahertz (THz) devices with high performance is in rapid ascent in order to promote applications of THz technology. In this paper, we propose a broadband, optically transparent and highly flexible multispectral beam splitter based on Ag nanowires/graphene (ANWG) composite film on polyethylene terephthalate film substrates. The properties of the ANWG-based beam splitters are investigated, which exhibit a broadband THz reflectance of about 90%, a high optical transmittance of over 86% in the visible range, and excellent mechanical flexibility. The THz experimental result of the ANWG-based beam splitter is close to those of numerical simulations using a theoretical model. In comparison with conventional THz beam splitters, the ANWG-based beam splitter possesses excellent light-splitting performances for both transmitting visible light and reflecting THz radiation, and the device can significantly improve the overall performance of THz optical systems. Moreover, the device can be effectively applied in the visible/infrared imaging systems to implement multispectral imaging. Our concept provides a promising route for realizing compact hybrid optical systems, and it has great potential for commercial applications.

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