Observation of Third Harmonic Generation in Two-Dimensional MoS2 Semiconductor Using Terahertz Free-Electron Laser

This study presents the third harmonic generation (THG) in two-dimensional MoS 2 deposited on Si/SiO 2 substrate. Intense terahertz pulses from a free-electron laser were used as pump. The pump central frequency is 3.5 THz, and the THG peak is observed around 10 THz. The THG intensity dependence on excitation density follows the $I_{3 \omega} \propto I_{\omega}^{3}$ relation which further confirms the THG.