ROTATION OF POLARIZATION PLANE OF PROBE FIELD BY LASER-INDUCED STRUCTURE IN HELIUM ATOM CONTINUUM

The ensemble of helium atoms in two electromagnetic fields has been investigated. The laser field coupling results in interference between two helium autoionizing states (AIS). The probe field scans the region of AIS and leads to photoionization. Rotating wave approximation was used to obtain the density matrix equation de­scribing the process. Nonlinear susceptibility of the atomic ensemble at the probe field frequency was found. Nonlinear effects such as polarization plane rotation and acquired ellipticity are calculated.