Optically Controlling Broadband Terahertz Modulator Based on Layer-Dependent PtSe(2) Nanofilms

In this paper, we propose an optically controlling broadband terahertz modulator of a layer-dependent PtSe(2) nanofilm based on a high-resistance silicon substrate. Through optical pump and terahertz probe system, the results show that compared with 6-, 10-, and 20-layer films, a 3-layer PtSe(2) nanofilm has better surface photoconductivity in the terahertz band and has a higher plasma frequency ω(p) of 0.23 THz and a lower scattering time τ(s) of 70 fs by Drude–Smith fitting. By the terahertz time-domain spectroscopy system, the broadband amplitude modulation of a 3-layer PtSe(2) film in the range of 0.1–1.6 THz was obtained, and the modulation depth reached 50.9% at a pump density of 2.5 W/cm(2). This work proves that PtSe(2) nanofilm devices are suitable for terahertz modulators.