# All-silicon terahertz metasurfaces for multi-focus multiplexed polarization generation

## TL;DR

This paper introduces all-silicon terahertz metasurfaces that can generate multiple polarization states and vector beams for advanced communication and secure information transmission.

## Contribution

The novel use of interleaved meta-atoms to combine geometric and propagation phase for multi-polarization and vortex beam generation.

## Key findings

- All-silicon metasurfaces enable independent control of phase and amplitude for different polarization states.
- Longitudinal multi-polarization vortex beams with unique topological charges are achieved under LCP illumination.
- The approach offers new possibilities for terahertz polarization manipulation and secure communication.

## Abstract

Polarization multiplexing enhances communication capacity but faces material limitations requiring complex device cascading. This paper proposes a strategy for generating multiple polarization states by combining geometric phase and propagation phase in spatially interleaved meta-atoms. This strategy enables the simultaneous generation of scalar (including linearly polarized, circularly polarized) and vector beams (VBs) in the transmitted wave, along with precise wavefront shaping capabilities for these distinct polarization states. Two all-silicon terahertz metasurfaces are designed that are capable of independently manipulating both the phase and amplitude of different polarization states in transmission. The first metasurface achieves focusing with multi-polarization states under left-handed circularly polarized (LCP) illumination, while the second realizes longitudinal focusing of vortex beams exhibiting multiple polarization states under LCP excitation, with each vortex beam carrying unique topological charges. This approach paves new avenues for advanced terahertz polarization manipulation, offering significant potential for next-generation communication and secure information transmission.

•Interleaved meta-atoms to generate multiple polarization states and vector beams•All-silicon metasurfaces enable independent control of phase and amplitude•Longitudinal multi-polarization vortex beams with unique topological charges under LCP

Interleaved meta-atoms to generate multiple polarization states and vector beams

All-silicon metasurfaces enable independent control of phase and amplitude

Longitudinal multi-polarization vortex beams with unique topological charges under LCP

Physics; optics; applied sciences