High-transmissivity Silicon Visible-wavelength Metasurface Designs based on Truncated-cone Nanoantennae

High-transmissivity all-dielectric metasurfaces have recently attracted attention towards the realization of ultra-compact optical devices and systems. Silicon based metasurfaces, in particular, are highly promising considering the possibility of monolithic integration with VLSI circuits. Realization of silicon based metasurfaces operational in the visible wavelengths remains a challenge. A numerical study of silicon metasurfaces based on stepped truncated cone shaped nanoantenna elements is presented. Metasurfaces based on the stepped conical geometry can be designed for operation in the 700nm to 800nm wavelength window and achieve full cycle phase response (0 to pi with an improved transmittance in comparison with previously reported cylindrical geometry [1]. A systematic parameter study of the influence of various geometrical parameters on the achievable amplitude and phase coverage is reported.