Linear-polarization duplexed metalens generate terahertz vortex by a silicon metasurface

All-dielectric metasurfaces can realize flexible full-vector manipulations of the complex optical field, without confronting the loss issues of plasmonic counterparts, and thus have been proposed for lots of nanophotonic functionalities. In this work, a silicon-bar metasurface is designed to generate multifunctional focusing characteristics, which act as duplexed metalens with unlocked topological charges of terahertz vortex for orthogonal linearly-polarized incident waves. It achieves full phase modulation by tuning lateral sizes of the bar without the anisotropic orientation requirement associated with the geometric phase, which is consequently of high efficiency since no polarization conversion is involved in this duplexed all-dielectric vortex metalens.(c) 2023 The Japan Society of Applied Physics