Investigation of planar photonic crystal band diagrams under the light cone using surface coupling techniques

We report experimental results for the band structure of 2-dimensional triangular photonic crystals etched in SOI wafers. Boundary conditions at the surface and at the border of the etched area of the slab, allow the excitation of guided modes via diffraction phenomena using surface coupling techniques and the determination of the structure band diagram above and below the light cone. These non-destructive techniques, usable for non-active materials, allow fast characterization of technical processes and the location in reciprocal space of areas with unique dispersion properties. PACS 42.70.Qs; 42.25.Fx; 81.70.Ex