Experimental observation of sub-radiant longitudinal mode and anomalous optical transmission in metallic wire meshes

Abstract

In conventional plasmonic media and plasmonic metamaterials, such as metallic wire meshes, a longitudinal mode of an electromagnetic wave manifests itself in frequency overlapping transverse modes, which impedes clear observation of longitudinal-mode-specific physical effects. Through interlacing two sets of wire meshes, an ideal band for the longitudinal mode is achieved ranging from zero frequency to plasma frequency, where transverse modes are completely forbidden. The unique spectral separation of modes facilitates the observation of pure longitudinal modes and related plasmonic effects in a bulk medium. We report the microwave experiment of anomalous optical transmission, induced solely by electromagnetic longitudinal mode resonance, below the plasma frequency in such a wire mesh medium.