Influence of polarization directions of the IR+XUV two-color laser fields on angle-resolved photoelectron energy spectrum.

By employing the frequency-domain theory, we investigate the influence of polarization directions on angle-resolved photoelectron energy spectrum in the above-threshold ionization (ATI) process of atoms exposed to the IR+XUV two-color laser fields, which shows the multiplateau structures. When the ionized electron is emitted along the IR laser's polarization direction, the width of each plateau keeps a certain energy range, and the jet structures and main lobes are determined by both the emission angle relative to the polarization direction of the XUV laser field and the number of the XUV photons absorbed by the electron. While when the ionized electron is emitted along the XUV laser's polarization direction, the width of each plateau depends on the polarization direction of the IR laser field, and the angular distribution of the ionized electron exhibits the isotropic characteristics. These results show that the ATI spectrum may be effectively controlled by changing the angle between the two laser fields' polarization directions.

Angular resolved above-threshold ionization spectrum of an atom in IR+XUV orthogonally polarized two-color laser fields.

We investigate the above-threshold ionization (ATI) process of atoms exposed to the IR+XUV orthogonally polarized two-color laser fields by using the frequency-domain theory. It is shown that there exists a dip structure in each plateau of the angular resolved ATI spectrum. The dip structure in the first plateau is attributed to the fact that the electron cannot absorb one XUV photon when its emission direction is perpendicular to the XUV laser polarization, while the one in the second plateau is attributed to the coherent results of different channels. The emergence of dip structure is associated directly with the XUV laser field. Furthermore, by applying the saddle-point approximation, it is found that the fringes on the spectrum is caused by the interference of two trajectories for different saddle-points in the IR laser field. Finally, it is found that, in the high energy region, the probability of ATI spectrum is mainly determined by the XUV laser field, and the width of each plateau is mainly determined by the IR laser field; on the other hand, the ATI spectrum of the low energy region is only determined by the IR laser field.