Flexible materials for terahertz optics: advantages of graphite-based structures

Flexible materials for applications in terahertz (THz) range imaging systems are investigated in this study. THz time-domain spectroscopy and THz imaging at 0.6 THz frequency are used to analyze optical properties of zone plates (TZP) with integrated cross-shaped filters, which are fabricated using direct laser writing on thin graphite, HB pencil-shaded graphite on paper, as well as reference metal-based and pure paper zone plates. Spectral features and focusing power comparable to the best metal-based TZP is achieved with graphite-based TZP. The pure paper and paper with pencil-shaded graphite TZPs showed increase in focusing power by a factor of similar to 1.5, supporting numerical 3D finite-difference time-domain simulations. The findings show that graphite-based TZPs can serve as a flexible, compact, and inexpensive optics elements for emerging THz imaging systems. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement