Transmission properties of a two-dimensional photonic crystal slab with an excitonic resonance

The transmission properties of a 2-D photonic crystal slab with an exciton resonance are investigated experimentally and theoretically. Good agreement between experiment and scattering matrix based theory is obtained. The photonic crystal slab is composed of a square lattice of etched square holes in a quartz substrate, filled by an inorganic-organic semiconductor and covered by a polystyrene guiding film. We demonstrate that the transmissivity of the structure shows pronounced dips, which originate from the excitation of quasi-guided modes in the photonic crystal slab. The measured and calculated angular dependence of the energy of these dips and their optical activity allow us to identify the physical properties of the quasi-guided modes, such as their symmetry and distribution of electromagnetic field.