Electron dynamics and optical properties modulation of monolayer MoS₂ by femtosecond laser pulse: a simulation using time-dependent density functional theory

In this study, we adopted time-dependent density functional theory to investigate the optical properties of monolayer MoS₂ and the effect of intense few-cycle femtosecond laser pulses on these properties. The electron dynamics of monolayer MoS₂ under few-cycle and multi-cycle laser irradiation were described. The polarization direction of the laser had a marked effect on the energy absorption and electronic excitation of monolayer MoS₂ because of anisotropy. Change in the polarization direction of few-cycle pulse changed the absorbed energy by a factor over 4000. Few-cycle pulse showed a higher sensitivity to the electronic property of material than multi-cycle pulse. The modulation of the dielectric properties of the material was observed on the femtosecond time scale. The negative divergence appeared in the real part of the function at low frequencies and photoinduced blue shift occurred due to Burstein-Moss effect. The irradiation of femtosecond laser caused the dielectric response within the infrared region and introduced anisotropy to the in-plane optical properties. Laser-based engineering of optical properties through controlling transient electron dynamics expands the functionality of MoS₂ and has potential applications in direction-dependent optoelectronic devices.