Characterization of the second- and third-order nonlinear optical susceptibilities of monolayer MoS2 using multiphoton microscopy

Abstract

We report second- and third-harmonic generation in monolayer MoS2 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 |χs(2)| = 2.0 × 10-20 m2 V-1 and, for the first time for monolayer MoS2, |χs(3)| = 1.7 × 10-28 m3 V-2. These sheet susceptibilities correspond to effective bulk nonlinear susceptibility values of |χb(2)| = 2.9 × 10-11 m V-1 and |χb(3)| = 2.4 × 10-19 m2 V-2, accounting for the sheet thickness. Experimental comparisons between MoS2 and graphene are also performed, demonstrating ∼3.4 times stronger third-order sheet nonlinearity in monolayer MoS2, highlighting the material's potential for nonlinear photonics in the telecommunications C band.