The creation and annihilation of pairs of optical vortices have been studied in transitions between patterns produced in a photorefractive oscillator. Smooth metamorphosis between stable patterns occurs through pair creation or annihilation but can be modeled using superposition of modes taking into account lifting of degeneracy of helical modes by helical astigmatism of the resonator. © 1996 The American Physical Society.

• Received 1 December 1995

DOI:https://doi.org/10.1103/PhysRevA.54.2369