Characterization of the second- and third-order nonlinear optical susceptibilities of monolayer MoS2 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 vertical bar chi((2))(s)vertical bar = 2.0 x 10(-20) m(2) V-1 and, for the first time formonolayer MoS2, vertical bar chi((3))(s)vertical bar= 1.7 x 10(-28) m(3) V-2. These sheet susceptibilities correspond to effective bulk nonlinear susceptibility values of vertical bar chi((2))(b)vertical bar= 2.9 x 10(-11m). V-1 and vertical bar chi((3))(b)vertical bar= 2.4 x 10(-19) m(2) V-2, accounting for the sheet thickness. Experimental comparisons between MoS2 and graphene are also performed, demonstrating similar to 3.4 times stronger third order sheet nonlinearity inmonolayer MoS2, highlighting the material's potential for nonlinear photonics in the telecommunications C band.