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Published April 1, 2004 | public
Journal Article Open

Mode matching interface for efficient coupling of light into planar photonic crystals


In order to integrate superdispersive elements based on photonic crystals, such as the superprism, with conventional integrated optics, insertion losses at the interface to the photonic crystal need to be reduced to an acceptable level. We describe a mode matching interface composed of cascaded diffraction gratings that generates the field profile of the photonic crystal Bloch mode from a slab mode. We calculate with three-dimensional finite-difference time-domain computation that by interposing such a multilayered grating between an unpatterned slab and a planar photonic crystal, the insertion efficiency is enhanced from 9% to 84%. Each diffraction grating consists of a row of holes and does not require any additional process steps from those used to fabricate the planar photonic crystal. In order to optimize the efficiency of the mode matching interface, constructive interference conditions are imposed between successive gratings and reflections from individual gratings are suppressed. We fabricate devices in silicon on insulator material and show experimental evidence of the Bloch mode structure and of the mode matching mechanism.

Additional Information

©2004 The American Physical Society (Received 19 September 2003; revised 25 November 2003; published 29 April 2004) The authors would like to thank Maxime Rattier for useful discussions. The authors wish to acknowledge generous support from DARPA under Contract No. N-00421-02-D3223, and the AFOSR under Contract No. F49620-03-1-0418.


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