Ellipticity dependence of nonperturbative harmonic generation in few-layer MoS2

Abstract

High-order harmonic generation in solid state materials is viewed as a means of studying strong field nonperturbative physics. Researching ellipticity dependence can help understand the dynamics of electron–hole pairs in the presence of strong laser field. In this work, ellipticity dependence of high harmonic generation in few layer MoS2 is experimentally investigated with a midinfrared laser centered at 3.9 um. We irradiate monolayer, bilayer and trilayer MoS2 with intense mid-infrared light to generate non-perturbative harmonics up to 11th order. We find that the normalized yield of each harmonic descends in a form of Gaussian-like profile as increasing the ellipticity of driving pulse. It is astonishing to see that ellipticity dependence of monolayer, bilayer and trilayer MoS2 follows the same rules. We ascribe this similarity to the same deviation distance of electron–hole pairs in three sets of samples. Meanwhile, the higher the harmonic order is, the more sensitive it is to ellipticity, which shows agreement with gas-phase harmonics. To explain the phenomena, we explore the role of intraband and interband dynamics with multiband semiconductor Bloch equations, which helps to delve deeper into ultrafast and strong-field features of MoS2.