Local characterization of transmission properties of a two-dimensional photonic crystal

We use a near-field scanning optical microscope to study optical transmission through a two-dimensional triangular photonic crystal. Spatial variations in the intensity of Light coupled through the sample depend on the photon energy and the numerical aperture of the collection optics. We discuss the relationship between the observed dependence and the local structure of the optical modes in the crystal. Features in the data arising from modes with Fourier components inside and outside the first Brillouin zone can be distinguished by this technique.