Generation and optical characterizations of metasurface with dumbbell shaped nano-cavity array

Metasurfaces with dumbbell shape have been rarely addressed so far and its polarization behavior is still unknown. This paper reports the fabrication of a dumbbell-shaped nano-cavity array as a 2D metasurface with an Al/dielectric/Al (MIM) configuration by electron-beam lithography, plasma etching, and self-aligned Al metallization. Monte Carlo simulation was applied to guide the lithography process in eliminating proximity effect for forming dumbbell shape, enabling reliable control by processing parameters. Both finite-difference time-domain (FDTD) simulation and experimental characterizations were carried out to investigate the optical polarization behavior across the visible and near-infrared wavelengths of the 2D metasurface with dumbbell shaped cells. Clear polarization sensitivity was observed, demonstrating the structural effect of the unit cell shape on the polarization property from ellipse to dumbbell. Further optimization work is still needed to enhance the polarization performance of such a 2D metasurface.