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Several novel spin-selected dual-wavelength metalenses have been proposed and investigated based on the plasmonic metasurface consisting of two kinds of rotary rectangle gap nanoantennas (RGN), which are designed based on merging two or four polarity-inverse lenses corresponding to different wavelengths (765 and 1300 nm). The spin-selected dual-wavelength metalenses with two similar and two different vertical and lateral focal points have also been proposed respectively, which can focus two wavelengths with inverse spin states to arbitrary special positions. The three-dimensional metalens with four focal points have also been proposed, which can focus four beams with inverse spin states and different wavelengths to preset positions. Moreover, a spin-dependent achromatic metalens has also been proposed, which can focus left circularly polarized (LCP) incidence with different wavelengths to the same position. Our work opens up new avenues toward establishing novel spin-selected and wavelength-selected metadevices, and is significant for the development of spin-controlled photonics and particles manipulation. In addition, it provides a new idea for solving the problem of data transmission from optical fiber communication to visible light communication.

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Several novel spin-dependent bi-functional metasurfaces consisting of different-sized rotary silicon nanobricks have been proposed and numerically investigated based on the Pancharatnam–Berry phase and structural phase simultaneously. Here, a transmission mechanism is strictly deduced, which can avoid crosstalk from the multiplexed bi-functional metasurface. Four kinds of high-efficiency bi-functional devices have been designed successfully at infrared wavelengths, including a spin-dependent bi-functional beam deflector, a spin-dependent bi-functional metalens, a bi-functional metasurface with spin-dependent focusing and deflection function, and a spin-dependent bi-functional vortex phase plate. All of the results demonstrate the superior performances of our designed devices. Our work opens up new doors toward building novel spin-dependent bi-functional metasurfaces, and promotes the development of bi-functional devices and spin-controlled photonics.

The polarization-independence optical metasurface has attracted great interests due to breaking the polarization limitations. In general, polarization-independence characteristics of metasurface almost always originates from the polarization-independence characteristics of the used resonant antenna itself. In this paper, a novel approach is proposed to achieve polarization-independence metasurface based on the irrotational nanobricks. Firstly, the intrinsic characteristics of a half wave plate has been invest igated, which can realize co-polarization transmission of X-linear-polarization (XLP) and Y-linear-polarization (YLP) lights, and cross-polarization transmission of circular polarization (CP) light, simultaneously. Eight high-efficiency silicon nanobricks with the phase shifts over 2  are designed as the basic unit cell, which have the same transmitted amplitude and phase for the CP and XLP light, and the ph ase difference for XLP and YLP light. We have also designed the beam deflector, metalens and vortex beam generator, which possess identical function for cross-polarized CP and co-polarized XLP and YLP light, respectively. These results can promote the deeper understanding of metasurface, and give a new method to design polarization-independent optical devices.