The dynamical behavior of optical vortices during propagation of an electromagnetic wave is investigated. The propagation of these waves is computed with rigorous scalar diffraction theory. It was observed that a single optical vortex propagates perpendicularly to the wave front. Two optical vortices with the same charges (isopolar vortex pairs) are observed to gyrate around each other during propagation. Two optical vortices with opposite charges (bipolar vortex pairs) are observed to drift laterally away from the general direction of propagation. In cases in which interference between waves is allowed to occur or in which wave fronts are converging to focal points, bipolar vortex pairs are sporadically created and annihilated. An elementary model for the propagation of vortex pairs is proposed to explain the gyration and drift phenomena.
© 1995 Optical Society of America
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