High-harmonic Generation With Counterrotating Circularly Polarized Laser Pulses In Solids

With the development of laser technology,nonlinear optical experiments have attracted great attention.In recent years,the nonlinear optical effect of high-harmonic generation has also been found in solids,which provides the possibility for the realization of compact attosecond light source,solid-state structure detection and ultra-fast optical switch.Thus,the high-harmonic generation in solids must be thoroughly studied,which is different from that in atoms and molecules.In addition to the interband polarization and the nonlinear intraband current generated by the acceleration of carriers in the bands,the scattering of electron/hole from neighboring atoms in solids can also be realized,which has an important effect on the generation of high-harmonic.In the interaction of strong laser field with atoms and molecules,high-energy photons can be emitted every half optical period,forming an attosecond pulse chain.An isolated attosecond pulse can be obtained by means of polarizing gating technique,which is of great significance for the study of electron dynamics in pump-probe experiments.However,due to the existence of different harmonic generation mechanisms in solids,it is still not clear whether this technology can be applied to high-harmonic generation in solids.The main contents of this paper are as follows:First,high-harmonic generation controlled by the intensity of polarization gating laser pulse is studied.It is found that high-harmonic can also be generated by circularly polarized laser fields due to the scattering of electron/hole from neighboring atoms in solids.This mechanism only exists in laser fields with high intensities,thus polarization gating technology is suitable for solid if the time delay of laser fields is increased;if the intensity of laser fields is reduced until the mechanism of scattering of electron/hole from neighboring atoms disappears,then the mechanism of high-harmonic generation is similar to that of atoms.In this case,the polarization gating technique is still applicable.Second,high-harmonic generated by counterrotating circularly polarized laser pulses with short duration and high intensity is studied.It is found that by controlling the time delay of the counterrotating circularly polarized laser pulses,different mechanisms can be selected from the high-harmonic generation in solids.By using laser pulse with high intensity,the mechanism of scattering of electron/hole from neighboring atoms is dominant.Therefore,the isolated attosecond pulses can be generated by manipulating the synthetic laser fields.