Determination of the band structure of photonic crystal waveguides

We report an experimental and theoretical investigation of the near infra-red reflectivity properties of two-dimensional (2D) periodically patterned semiconductor waveguides. The coupling of incident electromagnetic radiation to leaky modes of the photonic crystal waveguide is shown to clearly manifest itself by the appearance of sharp features in the reflectivity spectra. By determining the energy dependence of the resonant features on the angle of incidence along different symmetry directions we are able to map out the photonic band structure. Theoretical spectra obtained using an advanced scattering matrix theory are found to agree well with experiment. The vertical confinement provided by the waveguide is found to have a profound effect on the in-plane band structure of the photonic crystal.