Abstract

Nowadays the phenomenon of branch-point phase singularities in electromagnetic wave fields [1] is usually known as an optical vortex. Such vortex can be seen as a zero of a complex envelope of an optical field, which has a property that the field phase changes by 2πm around a closed loop containing the zero where the integer number m is so-called topological charge of the vortex. The parametric interactions may provide an efficient way of vortex transformation. The second harmonic, sum-frequency generation and parametric amplification were experimentally studied in [2]. It was shown that in this way it is possible to change topological charge and wavelength of the vortex. In the case of second harmonic generation (Soskin et. al) the resulted field consists two zeroes but their appearance was not related to walk-off.

© 1998 IEEE