Beam forming of light from structured metal nano-aperture vertical cavity lasers

We report the nano-scale patterning of concentric ring-shaped metal corrugations around a sub-wavelength aperture in Ag deposited on top of a vertical-cavity surface-emitting laser. The presence of the rings results in more than a doubling of collected far-field power and a reduction in far-field angular width from 100° to 28°. These nano-aperture lasers thus have the unique property of both a small near-field spot and a relatively low beam divergence. Finite-difference timedomain simulations confirm the experimental results and show that the far-field pattern is highly sensitive to misalignment of the aperture and to the presence of multiple transverse laser modes.