Transient non-linear optics of diamond under ultrashort excitation pulses

Abstract

Electronic response of crystalline diamond as well as high harmonic generation following irradiation by a single-cycle high-intensity laser pulse was calculated through modeling the dynamics in the framework of the time-dependent density functional theory. The frequencies of the applied laser pulses vary over visible regime with a timescale shorter than typical quantum dephasing. High harmonic yields, show substantial deviation from what is obtained from the power scaling law of perfect solids under longer cycle pulses due to the key role of strong nonlinear features of dynamics at high intensities. Further, the dynamical photon dressing of electronic states are monitored by Floquet quasi-static picture for ultrashort few cycle pulses. Our results show that dynamical bandgap is diminished as a function of increasing driven field frequency and the system changes into the dynamic metallization regimes that consequently leads to new hybridization of quasi static dressed bands particularly near high symmetrical points in the Brillouin zone. These Floquet hybridization can be used to produce coherent transport of charge on the scale of the huge number of lattice sites. Moreover, the pulse-induced phonon frequency variations that relate to bond softening and hardening, are connected to different order of Floquet dressed states. Importantly, it is found that dielectric response oscillation is directly proportional to the transient bandgap value so that entering into metallization mode preserves the polarization coherency. Based on the magnitude of calculated Keldysh parameter varies for dynamical bandgap, tunneling ionization is the dominant mechanism of excitation.