Study On Effects Of The Carrier-envelope Phase On The Photoelectron Energy Spectra With Low Intensity Laser Pulses

The advent and development of few-cycle laser pulses has greatly promoted the development of technologies associated with the strong-field physics and the attosecond science and the associated technologies.There are many highly nonlinear effects in the interaction process between strong few-cycle laser pulses and the atoms or molecules,such as high harmonic generation?HHG?,above-threshold ionization?ATI?,and non-sequential double ionization?NSDI?.Those processes all depend on the instantaneous electric field strength instead of the peak intensity of the laser pulse.For a few-cycle laser pulse,the instantaneous electric field strength is dependent on the phase of the carrier with respect to the envelope,i.e.,carrier-envelope phase?CEP?.Thus the CEP acts as a vitally important parameter for a few-cycle laser field.Up to now,a stabilized few-cycle laser pulse has been widely used to generate isolated attosecond pulses,to manipulate electron emissions,and to control molecular dissociations.Therefore the measurement of the CEP is significant for the strong-field physics.We study the CEP-dependent asymmetry spectra and CEP-dependent photoelectron energy spectra of a hydrogen atom in a few-cycle laser field from high intensity to low intensity by numerically solving the time-dependent Schr?dinger equation?TDSE?.We further show that the low-energy photoelectrons display distinct CEP-dependent intercycle interference fringes,providing an alternative way to retrieve the CEP with high sensitivity in a few-cycle laser field with low intensity,which is of great importance for the study and the measurement of the CEP.The contents of this thesis are shown in detail as follows.Much effort to date is focused on the effect of the CEP on the photoelectrons in the high laser intensity regime while little attention is paid to the low laser intensity regime.Indeed,a few studies focus on the important role of the CEP of a few-cycle laser field in the low intensity,but they mainly payed attention to the CEP effect of excited state populations and interference between multiphoton pathways.Up to now,the CEP effect on the high-energy photoelectron spectrum is rarely investigated in the low laser intensity regime.In this paper,we study the CEP-dependent asymmetry spectra and CEP-dependent photoelectron energy spectra of hydrogen atom in a few-cycle laser field in the intensity range of 2×10¹³W/cm²-1×10¹⁴W/cm² by numerically solving the time-dependent Schr?dinger equation?TDSE?.Both the asymmetry parameters and the photoelectron yields reveal clear oscillations with respect to the CEP,which depend sensitively on the electron energy and the laser intensity.At high laser intensities(>3×10¹³W/cm²),the yield of the high-energy photoelectrons shows two kinds of oscillations with the CEP for different electron energies.In contrast,at low laser intensities(<3×10¹³W/cm²),the oscillation of the high-energy photoelectron yield with the CEP is nearly the same for different electron energies.The oscillations for the higher-energy and lower-energy photoelectrons in the plateau region exhibit no clear phase shift,which will decrease the sensitivity of retrieving the single-shot CEP using the Steoreo-ATI method at low laser intensities.The low-energy photoelectrons show distinct CEP-dependent interference fringes.Based on a simple semiclassical model,we show that those fringes come from the intercycle interferences among electron wave packets emitted at time intervals separated by one laser cycle.Those CEP-dependent intercycle interference fringes might be used to retrieve the CEP in a few-cycle laser field with low intensity.The method operates simply with good stability and higher accuracy and it is less susceptible to the intensity averaging effect over the focal volume.The method makes up for the Stereo-ATI technologies in the low laser intensity with lower accuracy.