Direct determination of photonic band structure for waveguiding modes in two-dimensional photonic crystals

We directly determine the experimental photonic band dispersion structure of waveguiding modes under the light line in a two-dimensional photonic crystal (2D PhC) waveguide by using angle-resolved attenuated total reflection spectroscopy. Resonance coupling between the external evanescent wave from total reflection within the prism and the waveguiding modes in the 2D PhC provides clear information on individual band components by resolving the angle (i.e., wave vector k) and photon energy. The experimentally determined photonic band structure, which is essential for understanding the novel light propagation properties of PhC systems with many degrees of freedom, agrees well with the band structure predicted by theory. Furthermore, we demonstrate the accuracy and suitability of this method by analyzing field distribution and eigen-photon-energy calculations for a model structure identical to the experimental arrangement of the prism and sample structure.