The Photoelectron Angular Distribution Of The Ultrashort Pulse Phase Related Phenomena

With the development of laser technology, ultrashort laser pulses of a few cycles have been produced experimentally. More and more studies have been given to the interaction of ultrashort pulse with matter. Above-threshold ionization (ATI) is an important effect in research of laser-matter interaction, which means that atoms absorb more photons than it need to ionize. There are many new phenomena appear in ATI such as jet-structure, plateau-phenomena, inversion asymmetry and phase-dependent effect.This paper is about the study of phase-dependent effect of photoelectron of Kr atoms irridated by an infinite sequence of intense single-cycle pulses of circular polarization. We use nonperturbative, quantum scattering theory developed by Guo, Aberg and Crasemann which treats multi-photoion ization (MPI) as a scattering process in an isolated system that consists of photons and an atom within a framework of quantum electrodynmics. Energy is conserved throughout the interaction and the photoionization is a two-step process in which volkov state plays an important role: the first process is electrons ionize from atoms to volkov state, the second process is from volkov state to free electrons. The main results are as follows:Firstly, it was found that photoelectron angular distributions (PADs) in a single-cycle and circularly polarized laser pulse are anisotropic distributed and inversion asymmetric. The maximal ionization rate keeps constant with the varying absolute phase, but the position of maximal ionization, as well as the direction of symmetric axis of absolute phase, varies with the absolute phase. For , the number of photoelectrons ejected to the left direction is the same as that to the right direction.Secondly, we study the PADs in linearly bichromatic laser pulses. It is found that PADs are inversion asymmetric and depend on the phase difference of the two modes. and PADs is fourfold symmetric, for others it is two symmetric.PADs have jet-structure and broadening effect.In summary there is a one-to-one correspondence between the calculated PADs and the absolute phase, which makes it possible to determine the value of absolute phase of a laser pulse by detected PADs.