Perspectives on the application of InP-based photonic crystal waveguides for optical signal processing

Abstract

Photonic crystal waveguides have long attracted much attention in the integrated photonics community due to their high confinement properties and potential for the achievement of photonic circuits with a very high level of integration. While high propagation losses still impair most of the practical applications of such waveguides, predicted and demonstrated slow and dispersive propagation within compact lengths remain very attractive for optical signal processing. In this talk, results will be presented from an investigation on slow and dispersive propagation in two different types of InP-based photonic crystal waveguides fabricated at UCSB. Waveguides of the membrane type, with very strong vertical confinement, were fabricated and characterized, as well as guides with weak vertical confinement and deeply-etched holes. Those of the latter kind were successfully integrated with structures found in standard photonic circuits produced in our group. Detailed measurements of transmission will be presented showing slow and dispersive propagation close to band edges. Reasonable group delay enhancement is found, which is clearly dependent on propagation losses; on the other hand, extremely large GVD is found over reasonably wide bandwidths, even when considerable losses are present. This suggests that, by proper tuning of coupling coefficients, very compact dispersion-compensating elements can be designed. A discussion on the advantages and disadvantages, as well as different possibilities of using this class of waveguides for the implementation of delay lines and dispersion compensation will be presented.