Article abstract
Nature Photonics 2, 564 - 570 (2008)
Published online: 27 July 2008 | doi:10.1038/nphoton.2008.152
Subject Categories: Lasers, LEDs and light sources | Plasmonics
Small-divergence semiconductor lasers by plasmonic collimation
Nanfang Yu1, Jonathan Fan1, Qi Jie Wang1, Christian Pflügl1, Laurent Diehl1, Tadataka Edamura2, Masamichi Yamanishi2, Hirofumi Kan2 & Federico Capasso1
Abstract
Surface plasmons offer the exciting possibility of improving the functionality of optical devices through the subwavelength manipulation of light. We show that surface plasmons can be used to shape the beams of edge-emitting semiconductor lasers and greatly reduce their large intrinsic beam divergence. Using quantum cascade lasers as a model system, we show that by defining a metallic subwavelength slit and a grating on their facet, a small beam divergence in the laser polarization direction can be achieved. Divergence angles as small as 2.4° are obtained, representing a reduction in beam spread by a factor of 25 compared with the original 9.9-
m-wavelength laser used. Despite having a patterned facet, our collimated lasers do not suffer significant reductions in output power (
100 mW at room temperature). Plasmonic collimation provides a means of efficiently coupling the output of a variety of lasers into optical fibres and waveguides, or to collimate them for applications such as free-space communications, ranging and metrology.
- School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA
- Central Research Laboratory, Hamamatsu Photonics K.K., Hamamatsu 434-8601, Japan
Correspondence to: Federico Capasso1 e-mail: capasso@seas.harvard.edu
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