Theoretical Study On Resonant Enhancement Of The High-order Harmonic Generation In Solids By A Chirped Laser Pulse

The interaction between light and matter in an intense laser pulse has attracted extensive attention for researchers in recent years.As a new method to obtain X-ray light source,the high-order harmonics can used to generate the attosecond pulses.The attosecond time-scale pulses can detect the internal motion of electrons and track the ultrafast dynamics of atoms and molecules,which are important topics both theoretically and experimentally.The methods to improve the generation efficiency of the high-order harmonic generation(HHG)have become hot issues.Compared with the gas targets,HHG in solids have attracted much attention due to the higher electronic densities.We theoretically investigate the physical mechanism by adjusting the chirp parameters.In this work,we theoretically investigate the effect of the chirped laser pulse on the HHG in solids by solving the single-electron time-dependent Schrodinger equation(TDSE).We find a resonance peak,which becomes obvious with the increase of the chirp parameters.The position of the resonance peak is investigated by adjusting the laser wavelength.The energy corresponding to the resonance order remaines unchanged around 4.2 e V,which confirms that the resonance peak is dominated by the band gap emission.By the time-dependent population imaging(TDPI)and timefrequency(TF)analysis,we demonstrate that the resonance peak is caused by the Bloch oscillation between valance band(VB)and the conduction band(CB).