Excitation of radiative and evanescent defect modes in linear photonic crystal waveguides

The dispersion of line-defect modes in silicon-on-insulator photonic crystal waveguides is explored by means of angle- and polarization-resolved micro-reflectance measurements. The frequency-wave vector range accessible to the experiments is greatly expanded by the use of attenuated total reflectance, in addition to the standard one, thereby allowing one to study both truly guided (evanescent) and quasi-guided (radiative) photonic modes. The presence of a supercell repetition in the direction perpendicular to the line defect leads to the simultaneous excitation of defect and bulk modes folded in a reduced Brillouin zone. The group-velocity dispersion of defect modes corresponding to different polarizations of light is fully determined.