Multiwavelength Metasurfaces Based on Single-Layer Dual-Wavelength Meta-Atoms: Toward Complete Phase and Amplitude Modulations at Two Wavelengths

Since its invention, metasurface has been widely utilized to achieve nearly arbitrary wavefront control based on phase only modulation at single wavelength. To achieve better performance or exotic functions, it is desirable to demonstrate metasurfaces capable of realizing both phase and amplitude modulations. Meanwhile, the wavelength-dependent behavior of the metasurface is one of the critical limitations in existing metasurface structures. Specifically, single-layer metasurfaces with the capability to tailor both phase and amplitude at multiple wavelengths have not been reported so far. In this paper, a single-layer meta-atom is proposed which can realize ultrathin metasurfaces with complete phase and amplitude modulations at two THz wavelengths. Several dual-wavelength metalenses and a nondiffractive Airy beam generator operating at two THz wavelengths are numerically demonstrated, the simulated results of which are consistent with the theoretical calculations and design goals. The presented dual-wavelength meta-atom can provide a powerful building block in multiwavelength metasurface designs for controlling electromagnetic waves, including focusing, beam steering, beam generations, hologram, etc.