Characterization of the second- and third-harmonic optical susceptibilities of atomically thin tungsten diselenide

TL;DR

This study provides the first detailed measurement of the third-harmonic optical susceptibility of atomically thin tungsten diselenide, revealing its magnitude and polarization dependence, and compares it with second-harmonic susceptibility and other materials.

Contribution

It introduces a novel confocal microscopy method to characterize second- and third-harmonic susceptibilities in WSe2, providing new quantitative insights into its nonlinear optical properties.

Findings

Measured third-harmonic susceptibility $|_{s}^{(3)}| pprox 0.91 imes 10^{-28}$ m$^{3}$ V$^{-2}$

Found second-harmonic susceptibility $|_{s}^{(2)}| pprox 0.70 imes 10^{-19}$ m$^{2}$ V$^{-1}$

Susceptibility values are comparable to other transition metal dichalcogenides.

Abstract

We report the first detailed characterization of the sheet third-harmonic optical susceptibility, $\chi_{s}^{(3)}$, of tungsten diselenide (WSe$_{2}$). With a home-built confocal microscope setup developed to study harmonics generation, we map the second- and third-harmonic intensities as a function of position in the sample, pump power and polarization angle, for single and few layers flakes of WSe$_{2}$. We register a value of $|\chi_{s}^{(3)}| \approx$ 0.91 $\times$ 10$^{-28}$ m$^{3}$ V$^{-2}$ at a fundamental excitation frequency of $\hbar\omega$ = 0.8 eV, which is comparable in magnitude to the third-harmonic susceptibility of other group-VI transition metal dichalcogenides. The simultaneously recorded second-harmonic susceptibility is found to be $|\chi_{s}^{(2)}| \approx$ 0.70 $\times$ 10$^{-19}$ m$^{2}$ V$^{-1}$ in very good agreement on the order of magnitude with recent reports for WSe$_{2}$, which asserts the robustness of our values for $|\chi_{s}^{(3)}|$.