On angular coherent control of photocurrent caused by photoionization in a bichromatic laser field
Аннотация
A novel kind of coherent control of various atomic and molecular photoprocesses proceeding in a bichromatic electromagnetic (EM) laser field, angular coherent control, is proposed and demonstrated here theoretically by studying the particular case of negative-ion photodetachment in the field of a linearly polarized fundamental laser frequency and its second harmonic of arbitrary spatial configuration and orientation of the unit polarization vectors e1 and e2 of the respective harmonic fields. Due to the inherent spatial asymmetry of the applied bichromatic field, the ejection of detached photoelectrons is also generally asymmetric in respect of the detached photoelectron momentum replacement p→-p. As follows from our gauge-invariant analytical calculations within the framework of perturbation theory on EM interaction and a zero-range potential model for the negative ion, this field asymmetry results in a photocurrent, the magnitude and direction of which are strongly dependent on both the relative phase shift Φ between the harmonics of the ionizing bichromatic field and on the angle θ between the polarization vectors e1 and e2. The latter strong dependence on the angle θ is the background for angular control of the direction and magnitude of the produced photocurrent by means of an appropriate choice and proper adjustment of the angle between the polarization vectors of the incident bichromatic field harmonics.