We calculate linear and nonlinear optical susceptibilities arising from the excitonic states of mono- layer MoS2 for in-plane light polarizations, using second-quantized bound and unbound exciton operators. Optical selection rules are critical for obtaining the susceptibilities. We derive the valley-chirality rule for the second harmonic generation in monolayer MoS2, and find that the third- harmonic process is efficient only for linearly polarized input light while the third-order two photon process (optical Kerr effect) is efficient for circularly polarized light using a higher order exciton state. The absence of linear absorption due to the band gap and the unusually strong two-photon third-order nonlinearity make the monolayer MoS2 excitonic structure a promising resource for coherent nonlinear photonics.
@article{arxiv.1711.10513,
title = {Optical nonlinearities of excitons in monolayer MoS2},
author = {Daniel B. S. Soh and Christopher Rogers and Dodd J. Gray and Eric Chatterjee and Hideo Mabuchi},
journal= {arXiv preprint arXiv:1711.10513},
year = {2018}
}