A narrow pulse width and high peak power passively Q-switched laser based on the saturable-absorption characteristic of 2-layer TeSe2

Abstract

Group-VI binary compounds have attracted much attention owing to their intriguing photoelectric properties but are rarely applied in laser Q-switching technology. In this work, by theoretically analysing the match of a layered structure with laser wavelength, the excellent Q-switching effect based on 2D TeSe₂ was experimentally obtained. Energy-band diagrams of bulk and layered TeSe₂ were calculated with first principles calculations, which led to the experimental preparation of 2-layer TeSe₂ for saturable absorption with transition across the band gap. Through the measurement and analysis of nonlinear transmittance with 1 μm laser, the 2-layer TeSe₂ sample was found to have a high modulation depth of 16.1%, an excited-state lifetime of 444 μs, and a nonlinear absorption coefficient of −3.24 × 10³ cm GW⁻¹. A 2-layer TeSe₂ passively-Q-switched 1 μm laser was finally realized experimentally, generating a pulse with a minimum 47.25 ns temporal width. Owing to the narrow pulse and low pulse repetition, 94.08 W peak power was obtained, which is the highest value from 2D SA passively-Q-switched solid laser as far as we know.