’Dark Beams’ Revealed

Researchers have tried to demystify the presence of "dark beams," complex arrays that result from emissions of broad-area vertical-cavity surface-emitting lasers.

A team from Haifa University in Israel discovered that these dark spot arrays consist of multiple, closely packed optical vortices. Optical vortices are optical fields that have phase singularities and show increased complexity as the injection current level is raised.

The group observed that most of these light distributions are not the result of multifrequency operation, but exhibit single-frequency characteristics. The dark beam patterns seem to emanate from a spontaneous process of transverse mode-locking, assisted by the laser's nonlinearity. Surprisingly, these patterns show a high resemblance to patterns generated in other nonlinear scenarios that are completely different both in scale and in mechanism.

The ability to spontaneously generate controlled and stable vortex arrays in a miniature cavity device could lead to commercial applications such as dynamic optical storage. Further explanation of the team's research appears in the July 9 issue of Science.