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Small-divergence semiconductor lasers by plasmonic collimation

Nature Photonics volume 2, pages 564570 (2008) | Download Citation

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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-µm-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.

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Acknowledgements

We acknowledge support from the Air Force Office of Scientific Research (AFOSR MURI on Plasmonics) and the Harvard Nanoscale Science and Engineering Centre (NSEC). This work was performed in part at the Centre for Nanoscale Systems (CNS) at Harvard University, a member of the National Nanotechnology Infrastructure Network (NNIN), which is supported by the National Science Foundation under NSF award no. ECS-0335765. CNS is part of the Faculty of Arts and Sciences at Harvard University. We would like to thank H. Mosallaei for helpful discussions and suggestions. We acknowledge the contributions of R. Blanchard in the preliminary simulations of the ring-shaped collimators.

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Affiliations

  1. School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA

    • Nanfang Yu
    • , Jonathan Fan
    • , Qi Jie Wang
    • , Christian Pflügl
    • , Laurent Diehl
    •  & Federico Capasso
  2. Central Research Laboratory, Hamamatsu Photonics K.K., Hamamatsu 434-8601, Japan

    • Tadataka Edamura
    • , Masamichi Yamanishi
    •  & Hirofumi Kan

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Correspondence to Federico Capasso.

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DOI

https://doi.org/10.1038/nphoton.2008.152

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