Spin-Decoupled Multifunctional Metasurface for Asymmetric Polarization Generation

Abstract

Integrating multiple functionalities into a single device is a striking field in metasurfaces. One promising aspect is polarization-dependent meta-devices enabled by simultaneous phase control for orthogonally polarized waves. Among these, Pancharatnam-Berry (PB) metasurfaces have drawn enormous interest owing to their natural and robust phase control ability over different circularly polarized waves. However, the phase responses are locked to be opposite with each other, resulting in interrelated functionalities under the circularly polarized incidence. Here, a generic designing method based on transmission-type dielectric metasurfaces is proposed in the terahertz regime, which breaks this relation by further incorporating dynamic phase with geometric phase, namely, spin-decoupled phase control method. We demonstrate this method by designing and characterizing an efficient multifunctional meta-grating, which splits different circularly polarized waves to asymmetric angles under normal incidences. More importantly, we promote this method by designing several multiplexed meta-gratings for applications of asymmetric polarization generation, which can convert arbitrary linearly polarized wave to two different linearly polarized waves with nearly equal strength and split them to asymmetric angles with a polarization-insensitive efficiency. The designing strategy proposed here shows an impressive robustness and a great flexibility for designing multifunctional metasurface-based devices and opens new avenues toward modulation of polarization states and the application of metasurfaces in beam steering and polarization multiplexing systems.

High-efficiency metadevices for bifunctional generations of vectorial optical fields

“…In this paper, we study reflective metasurfaces as an example to illustrate our key idea and extensions to the transmissive case are straightforward. To realize such spin-delinked dual functionalities, our meta-atoms should exhibit both spin-dependent geometric phases and spin-independent resonant phases, as already pointed out in recent literature [33,35,39,46,51,52]. Moreover, to generate a predesigned polarization distribution in the VOF, our meta-atoms should further possess desired local polarization-control capabilities, corresponding to certain paths on Poincare's sphere (see Figure 1a).…”

“…Designing metasurfaces to exhibit certain anisotropic or spatially inhomogeneous phase distributions for reflected/transmitted waves, researchers have demonstrated separate manipulations on polarization [10][11][12] or wave front [13][14][15][16][17][18] properties of EM waves, leading to many practical applications (e.g., polarization control [10][11][12], light-bender [13][14][15][16][17], metalens [19][20][21][22][23], and metahologram [24][25][26][27]). More recently, metadevices exhibiting combined functionalities of polarization and wave front manipulations were proposed [18,[28][29][30][31][32][33][34][35][36][37][38][39], some of which could already generate particular VOFs as desired [29][30][31][37][38][39][40]…”

Polarization‐Sensitive Dielectric Membrane Metasurfaces

“…[27,30] Another efficient solution for applications is to use polarizationdependent meta surfaces. [31][32][33][34] By interleaving the device designs for orthogonal polarization states or designing the polarizationselective meta atom, such as elliptical and rectangular disks or holes, [35][36][37] a metasurface can show distinct functionalities under varying inci dent polarizations.…”

Generation of terahertz vector beams using dielectric metasurfaces via spin-decoupled phase control

“…Recently, metasurfaces have attracted immense interest owing to the unprecedented light manipulating ability in a subwavelength resolution [21], which allows pixelated and simultaneous control over the interfacial phase, polarization and amplitude distributions of light at will, serving as a new and promising platform for designing next-generation ultrathin devices, such as anomalous deflectors [22][23][24], lenses [25][26][27], holograms [28][29][30], polarization generators and analyzers [31][32][33][34], surface plasmon couplers [35,36], and special beam generators [22,25,37,38], including CVB generators [39][40][41][42][43]. Among the reported metasurface-based CVB generators, geometric phase method is widely applied owing to its flexible phase control mechanism and convenient polarization reorganization ability in circular polarization basis, such as generating vector vortex beams (VVBs) [44].…”

“…Multiplexed method can accomplish these tasks, however, the cost is the reduction of the efficiency. To overcome this problem, it is crucial to introduce dynamic phase control at the same time to decouple the phase responses of the two circularly polarized components [32,42,45].…”