Nonlinear effect of self-induced variations of polarization of tightly focused laser beams

There are presented results of theoretical investigation of nonlinear self-depolarization effect resulting in variation of space distribution of polarization-ellipse parameters of high-intensity focused laser beam. In particular, both linear and circular initial polarizations are shown to change and turn into elliptic polarization with inhomogeneous distribution of polarization-ellipse parameters in focal area. Detailed results and calculations are presented for particular case of Gaussian beams of low order. Bearing in mind obtained results, we discuss specific symmetry structure of self-depolarization effect allowing experimental checking of described phenomenon. There are analyzed and estimated other contributions to depolarization effect resulting from low-intensity diffraction. Possibility of observing polarization dependence for damage and self- focusing threshold in transparent materials is also considered.