Optical second harmonic generation in thin-films of MoS2

Our experiment shows that monolayer molybdenum disulfide (ML MoS₂) has big second-order non-linear susceptibility, which allows strong second harmonic generation. As the SHG has relations with the structure of crystal, we can identify the crystal's orientation by detecting the angle dependency of SHG. We rotate the MoS₂ and find the intensity of SHG has a period of 60° , which follows the symmetry of structure. At last, to detect the integrality of crystal, we perform two SHG mappings.