Characterization of the second- and third-order nonlinear optical susceptibilities of monolayer MoS 2 using multiphoton microscopy

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 | \ ^ (2) | \\ =2. 0\ 10^-20 m2 V−1 and, for the first time for monolayer MoS2, | \ ^ (3) | =1. 7\ 10^-28 m3 V−2. These sheet susceptibilities correspond to effective bulk nonlinear susceptibility values of | \ ^ (2) | =2. 9\\ \ 10^-11 m V−1 and | \ ^ (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.