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▲ [10p-N404-6] Mid-infrared extraordinary transmission through gold-covered dielectric microsphere monolayer
Keywords:Extraordinary transmission, gold-covered dielectric microsphere monolayer
Extraordinary optical transmission (EOT), originally reported by Ebbesen et al., is a phenomenon that electromagnetic waves pass through small holes periodically perforated in a metallic film with high transmittance. The EOT is usually observed as a transmittance peak in the visible and the near infrared regime. Here we report EOT through gold-covered silica-microsphere monolayer in the mid-infrared region (5-25 mm), which is an important wavelength region for vibration spectroscopy and the black-body radiation at the room temperature. Although the entire surface appears to be covered with a thin gold film when viewing from above, the transmittance is much higher than that of a flat gold film with the same thickness. Calculations based on the finite different time domain (FDTD) method revealed that the EOT is caused by light passing between the gold film on the substrate and that on the microsphere, and the gold capped sphere acts as an optical antenna, resulting in the efficient transmission of light.