Experimental observation of intermodal dispersion in photonic crystal directional couplers

Abstract

The intrinsic multimode nature of a directional coupler responsible for its functionality leads to intermodal dispersion. In this work, the authors experimentally demonstrate at microwave frequencies that the energy components of a pulse coupled to each of the supermodes of the photonic crystal directional coupler travel at different velocities. An intermodal dispersion of 5 ns/m is measured, which is in good agreement with the theoretical results. This value is more than two orders of magnitude higher than that reported from conventional two-core fiber couplers.