Localized vortices in semiconductor lasers

Description

Beyond the chirality of light associated to polarization or spin, light beams can carry an additional orbital angular momentum due to the helicoidal structure of their phase front. This property, if combined with light localization could give rise to localized optical vortices, whose existence in nonlinear and dissipative optical systems is suggested by several theoretical studies. However, while several kinds of localized states have been experimentally found, no observation of localized vortices have been reported to date. We demonstrate the existence of bistable and addressable chiral localized structures in a semiconductor laser with saturable absorber. For a fixed set of parameters, we observe localized states with positive or negative topological charge, both coexisting with a fundamental "off" state. In contrast with phase defects and vortex solitons, the spatial structures described in this report are transversally localized and bistable due to the presence of dissipation. These properties, generically associated to localized structures, make localized vortices attractive for the realization of arrays of independant and controllable "doughnut shaped" beams which would dramatically enhance the efficiency of advanced optical nanoscopy techniques, especially in fast and compact sources such as semiconductor lasers.

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