We investigate wave propagation with opposite energy and phase velocity at the surface of a two-dimensional photonic crystal. We introduce a surface defect based on a terminating row rich in material. We show how this type of defect induces surface modes with dispersion that can be flexibly manipulated. We observe the formation of single or multiple surface bands coming from the upper periodic band with a negative or a positive band slope. We perform a numerical experiment, realizable at mid- and near-infrared frequencies, which unambiguously verifies in a direct fashion the forward or backward type of propagation of the excited surface wave. Our numerical results demonstrate the existence of backward-propagating surface waves stemming from bands with a negative slope. This study may aid the design of subdiffraction plasmon based guiding devices.

• Received 31 October 2006

DOI:https://doi.org/10.1103/PhysRevB.75.245116