Hosna Sultana1
University of Alabama1
Recent advancements of optically thin metasurfaces enable us to explore and devise the critical limit of light-matter interaction. With the abrupt phase change at the interface of two media at the subwavelength scale, the metasurface can dictate light’s chirality, polarization, beam steering, resonance coupling, and plasmonic super focusing. Out of diverse design, GSP metasurface has gained much attention due to plasmon-enhanced scattering, absorbing, and polaritonic functionality in the optoelectronic device. Many research have been done to tune this metal-dielectric metasurface configuration, yet there has not been a full understanding of how the plasmonic effect of a structured metal and dielectric cavity control evanescent field towards Surface Wave (SW) propagation, Electro-magnetically Induced Absorption (EIA), and SPP generation, especially visible wavelength. In this work, we investigated the coupling effect of the GSPs modes in the case of phase gradient metasurface which consists of the anisotropic metal nanoantenna. With Finite Difference Time Domain (FDTD) simulation, we studied how simple geometric variation of nanoantenna’s length, this asymmetric structure could channel light from broadband (650-850) anomalous beam steering to SW and generate SPP for the normal incidence light at visible wavelength. We also study the band structure and dispersion relation for the unit cell to detect the localized and propagating optical modes. We further relate the result of the wavelength-dependent complex pattern of symmetric and asymmetric SPP mode excitation in the different regions of nanoantenna that originate due to asymmetric structure. The hybridization SPP mode by coupling across the dielectric cavity opens more possibilities of exploring the net effect of surface wave propagation in various dielectric cavity structures and tuning lots of interesting near field phenomena in plasmonic metasurfaces.