Mu-Negative and Near-Zero Lined Disks for Surface-Enhanced Mid-Infrared Spectroscopy

We report a novel resonant metasurface (MTS) based on mu-negative and near-zero (MNNZ) metamaterial (MTM)-lined disks for improved surface-enhanced mid-infrared spectroscopy, which relies on the strong electric-field enhancement near plasmonic metals. The design consists of an array of gold disks patterned with meandered capacitive gaps using electron-beam lithography on a ZnSe substrate. These gaps allow the electric field to be enhanced over a much wider area. The MNNZ MTM-lined disk MTS operates at a wavelength of $15\ \mu\mathrm{m}$ (667 cm-1 or 20 THz) with miniaturized, polarization-insensitive unit cells that exhibit plasmonic-like field enhancement of > 30 over a wide area. In this operation band, the MTS may be applied to CO 2 detection with enhanced sensitivity and subwavelength resolution.