Combination of high-intensity femtosecond laser pulses for generation of time-dependent polarization pulses and ionization of atomic gas

Abstract

Time-dependent polarization pulses are generated by combining two perpendicularly polarized, high-intensity laser pulses. The time evolution of the polarization state of the combined laser pulse is measured by the POLLIWOG technique. We observed changes in the polarization state while varying the relative delay. In order to investigate the effect of pulse combination on the ionization of atoms, the electron signals and the ion signals are measured by irradiating combinations of two perpendicularly polarized pulses or two parallel polarized pulses. With the two parallel polarized pulses, high-order fringe-resolved autocorrelations are obtained by measuring the time-integrated ion signals as a function of the time delay. When two perpendicularly polarized pulses are combined, the fringe period of the time-integrated electron signal as a function of the time delay is different from that of the time-integrated ion signal. This is due to the fact that the electron signal depends on the direction of the field vibration and the number of generated electrons. We also measured the electron energy distributions at different relative delays and confirmed that these depend on the polarization state of generated pulses.