We provide experimental and theoretical proof that higher-order optical vortices are intrinsically unstable. Being very susceptible to field perturbations, the main vortex tends to split up into singly charged optical vortices, giving rise to a fine structured dark region in the core of the carrying singular beam. The present work describes three different experimental methods that allows to observe this vortex-splitting phenomenon, the first two being based respectively on intensity and phase maps of the vortices, while the third one consists on observing the far-field interference pattern behind a screen where a set of multiple pinholes are symmetrically arranged over a circle. This device, called multi-pinhole interferometer, turned out to be a powerful tool to study very ‘dark’ regions of the electromagnetic field and to provide a local decomposition of arbitrary optical fields in the basis of orbital angular momentum states. Finally, we also provide a theoretical framework that explains this vortex-splitting phenomenon, revealing its practically unavoidable nature.


Seminar, October 11, 2013, 10:30. Seminar Room

Hosted by Prof. Romain Quidant