Carrier-envelope phase dependence of non-sequential double ionization in few-cycle pulses.

The influence of carrier-envelope phase (CEP) of a few-cycle laser pulse on non-sequential double ionization (NSDI) of an atom is investigated by applying the three-dimensional semi-classical re-scattering method. The asymmetric momentum distribution of the double-charged ion parallel to the laser polarization, which depends on the CEP, is explained by comparing the contributions from several half-cycles in the laser pulse. The ionization rate and the returning kinetic energy of the first electron dramatically affect the contributions from each half-cycles, and play different roles in different laser intensity regimes.

[Optics heterodyne detection of the autoionization state of barium].

The autoionization state of barium was observed by optics heterodyne between three-photon resonant nondegenerated six-wave mixing (NSWM) and two-photon resonant nondegenerated four-wave mixing (NFWM). In this way, optics heterodyne spectrum of 6p(3/2) 19d autoionization state of barium was measured. The suppression and enhancement of the NFWM signal was observed which was caused by the quantum interference between NFWM and NSWM.

Generalized n-photon resonant 2n-wave mixing in an (n+1)-level system with phase-conjugate geometry.

A generalized scheme for phase-conjugate resonant 2n-wave mixing, which has a high efficiency and is easy for phase matching, is proposed. As a new type of coherent laser spectroscopy this approach can be employed for studying highly excited atomic states or states with a high angular momentum. To demonstrate its feasibility we have studied the doubly excited autoionizing Rydberg states of Ba by phase-conjugate six-wave mixing, and have furthermore achieved eight-wave mixing in Na.

Theory of the Kapitza-Dirac diffraction effect.

We treat the Kapitza-Dirac diffraction effect observed recently by Batelaan et al. using a newly developed nonperturbative quantum-field scattering theory. Our theory shows that an electron beam passing perpendicularly through a focused standing light wave can produce diffraction patterns.

Rayleigh-type nondegenerate four-wave mixing: ultrafast measurement and field correlation.

We report on an ultrafast longitudinal time measurement by a nonresonant Rayleigh-type nondegenerate four-wave mixing (NFWM). We investigated the field-correlation effects on Rayleigh-type NFWM by examining the time-delayed dependence of the NFWM spectra. Based on the field-correlation effects, a time-delayed method is proposed to suppress the thermal effect, and ultrafast relaxation time can be measured even in an absorbing medium.