Characterization of the second- and third-order nonlinear optical susceptibilities of monolayer MoS$_2$ using multiphoton microscopy

TL;DR

This study uses multiphoton microscopy to measure and compare the second- and third-order nonlinear optical susceptibilities of monolayer MoS₂, revealing its strong nonlinear response suitable for photonics applications.

Contribution

First precise measurement of third-order nonlinear susceptibility in monolayer MoS₂, establishing its potential for nonlinear photonics and providing a detailed characterization method.

Findings

Monolayer MoS₂ exhibits strong third-order nonlinearity.

Quantified second- and third-order sheet susceptibilities.

MoS₂'s third-order nonlinearity is ~3.4 times stronger than graphene.

Abstract

We report second- and third-harmonic generation in monolayer MoS$_\mathrm{2}$ as a tool for imaging and accurately characterizing the material's nonlinear optical properties under 1560 nm excitation. Using a surface nonlinear optics treatment, we derive expressions relating experimental measurements to second- and third-order nonlinear sheet susceptibility magnitudes, obtaining values of $|\chi_s^{(2)}|=2.0\times10^{-20}$ m$^2$ V$^{-1}$ and for the first time for monolayer MoS$_\mathrm{2}$, $|\chi_s^{(3)}|=1.7\times10^{-28}$ m$^3$ V$^{-2}$. These sheet susceptibilities correspond to effective bulk nonlinear susceptibility values of $|\chi_{b}^{(2)}|=2.9\times10^{-11}$ m V$^{-1}$ and $|\chi_{b}^{(3)}|=2.4\times10^{-19}$ m$^2$ V$^{-2}$, accounting for the sheet thickness. Experimental comparisons between MoS$_\mathrm{2}$ and graphene are also performed, demonstrating $\sim$3.4 times stronger third-order sheet nonlinearity in monolayer MoS$_\mathrm{2}$, highlighting the material's potential for nonlinear photonics in the telecommunications C band.