Polarization-selective terahertz vortex zooming via rotational metasurfaces

While dynamically tunable polarization-selective manipulation holds transformative potential for emerging terahertz (THz) communication systems, conventional metasurfaces are fundamentally limited by static operation that constrains their adaptability across multifunctional application scenarios. Here, we introduce a mechanically reconfigurable cascaded metasurface enabled by rotational actuation. By selecting silicon pillars with polarization-filtering properties for Layer I (M1) and polarization-maintaining properties for Layer II (M2), the device simultaneously achieves polarization-discriminated vortex beam generation and continuous focal tuning. Experimental results show that under y-polarized excitation, it produces focused vortex beams within the cross-polarized channel while maintaining remarkably low crosstalk levels (<-13.11 dB) and achieving high mode purity (71.21%). By rotating M2 from 90° to 180°, experimental results demonstrate continuous zooming of the focal spot from 8.721 mm to 4.209 mm, accompanied by an increase in the numerical aperture (NA) from 0.567 to 0.819. This integrated design offers a viable solution for real-time polarization-resolved beam shaping in adaptive THz systems.