On angular coherent controlof photocurrent caused by photoionization in a bichromatic laserfield

Abstract

A novel kind of coherent control of various atomic and molecularphotoprocesses proceeding in a bichromatic electromagnetic (EM) laserfield, angular coherent control, is proposed and demonstratedhere theoretically by studying the particular case of negative-ionphotodetachment in the field of a linearly polarized fundamental laserfrequency and its second harmonic of arbitrary spatial configuration andorientation of the unit polarization vectors e1 and e2 ofthe respective harmonic fields. Due to the inherent spatial asymmetry ofthe applied bichromatic field, the ejection of detached photoelectrons isalso generally asymmetric in respect of the detached photoelectronmomentum replacement p→-p. As follows from ourgauge-invariant analytical calculations within the framework ofperturbation theory on EM interaction and a zero-range potential modelfor the negative ion, this field asymmetry results in a photocurrent,the magnitude and direction of which are strongly dependent on both therelative phase shift Φ between the harmonics of the ionizingbichromatic field and on the angleθ between the polarization vectors e1 and e2. Thelatter strong dependence on the angle θ is the background for angular control of the direction and magnitude of the producedphotocurrent by means of an appropriate choice and proper adjustment ofthe angle between the polarization vectors of the incident bichromaticfield harmonics.