Broadband nonlinear optical resonance and all-optical switching of liquid phase exfoliated tungsten diselenide

TLDR

Tungsten diselenide (WSe₂), a two‑dimensional transition‑metal dichalcogenide, is prized for its gapped electronic structure, high carrier mobility, and valley pseudospin, yet its nonlinear optical properties remain underexplored. This work systematically investigates the spatial self‑phase modulation and distortion effects in WSe₂ ethanol suspensions, targeting the nonlinear refractive index and third‑order optical response. The authors elucidate the SSPM distortion mechanism in WSe₂ dispersions and compute the wavelength‑dependent nonlinear refractive index n₂ and third‑order susceptibility χ^(3) under 457 nm, 532 nm, and 671 nm excitation. They experimentally demonstrate broadband all‑optical switching of two laser beams via spatial cross‑phase modulation, highlighting the material’s strong nonlinear response and its potential for future all‑optical devices.

Abstract

As a kind of two-dimensional transition metal dichalcogenide material, tungsten diselenide (WSe2) has attracted increasing attention, owing to its gapped electronic structure, relatively high carrier mobility, and valley pseudospin, all of which show its valuable nonlinear optical properties. There are few studies on the nonlinear optical properties of WSe2 and correlation with its electronic structure. In this paper, the effects of spatial self-phase modulation (SSPM) and distortion influence of WSe2 ethanol suspensions are systematically studied, namely, the nonlinear refractive index and third-order nonlinear optical effect. We obtained the WSe2 dispersions SSPM distortion formation mechanism, and through it, we calculated the nonlinear refractive index n2, nonlinear susceptibility χ(3), and their wavelength dependence under the excitation of 457 nm, 532 nm, and 671 nm lasers. Moreover, by use of its strong and broadband nonlinear optical response, all-optical switching of two different laser beams due to spatial cross-phase modulation has been realized experimentally. Our results are useful for future optical devices, such as all-optical switching and all-optical information conversion.