We experimentally study the fields close to an interface between two photonic crystal waveguides that have different dispersion properties. After the transition from a waveguide in which the group velocity of light is vg∼c/10 to a waveguide in which it is vg∼c/100, we observe a gradual increase in the field intensity and the lateral spreading of the mode. We attribute this evolution to the existence of a weakly evanescent mode that exponentially decays away from the interface. We compare this to the situation where the transition between the waveguides only leads to a minor change in group velocity and show that, in that case, the evolution is absent. Furthermore, we apply novel numerical mode extraction techniques to confirm experimental results.

dx.doi.org/10.1364/OL.36.001170
Opt. Lett.

Spasenović, M, White, T. P, Ha, S, Sukhorukov, A. A, Kampfrath, T, Kivshar, Y. S, … Kuipers, L. (2011). Experimental observation of evanescent modes at the interface to slow-light photonic crystal waveguides. Opt. Lett., 36(7), 1170–1172. doi:10.1364/OL.36.001170