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

Abstract

We report second- and third-harmonic generation in monolayer MoS${}_2$ 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 $|{\chi }_s^{(2)}|=2.0\times 10^{-20}$ m${}^2$ V${}^{-1}$ and for the first time for monolayer MoS${}_2$, $|{\chi }_s^{(3)}|=1.7\times 10^{-28}$ m${}^3$ V${}^{-2}$. These sheet susceptibilities correspond to effective bulk nonlinear susceptibility values of $|{\chi }_b^{(2)}|=2.9\times 10^{-11}$ m V${}^{-1}$ and $|{\chi }_b^{(3)}|=2.4\times 10^{-19}$ m${}^2$ V${}^{-2}$, accounting for the sheet thickness. Experimental comparisons between MoS${}_2$ and graphene are also performed, demonstrating $\sim$3.4 times stronger third-order sheet nonlinearity in monolayer MoS${}_2$, highlighting the material's potential for nonlinear photonics in the telecommunications C band.

Accepted by 2D Materials, 28th Oct 2016