Fano interference in Extraordinary Optical Transmission

We analyze the lineshape of the extraordinary optical transmission (EOT) associated with surface plasma waves (SPWs) excited with a metal photonic crystal (MPC), an Au film perforated with a 2.6 µm period, two-dimensional array of holes, integrated atop a GaAs substrate. From its asymmetry by Fano interference between transmission mediated by SPWs and direct transmission through individual holes, the resonance energy of the fundamental SPW propagating along the MPC/GaAs interface is extracted as 138.8 meV. This energy, the reference of the analysis, is slightly higher than the energy of the apparent peak of the EOT but lower than that of the Rayleigh anomaly closely related to the direct transmission. Its accuracy is verified with an identical MPC integrated on a quantum dot infrared photodetector coupled to the same SPW. Additional lineshape parameters, including relative strength of the two pathways to the transmission and SPW broadening, are determined from experiments. A condition of the Fano interference for EOT, critical to the intensity of its peak transmission, is established with their relations.