Cascaded Metasurfaces With Polarization Multiplexing for Channel-Separated Terahertz Beam Steering

Conventional adaptive dynamic beam steering schemes suffer from excessive complexity, large volume, and high power consumption. Meanwhile, dynamically tunable metasurfaces lack mature material systems optimized for high frequency terahertz (THz) operation, restricting their practical application. To solve these limitations, we propose a polarization multiplexed cascaded metasurface (PMCM) for adaptive THz beam steering. The joint phase distribution of this design strategy is realized via the linear superposition of the phase distributions of the two cascaded layers, which obviates the need for complex local phase adjustment using active components. One with rectangular pillars enable spin-decoupled phase modulation, allowing lens phases, gradient phases, and vortex phases to be embedded in orthogonal circular polarization (CP) channels; the other type is cylindrical dielectric pillars, which are used to maintain polarization-insensitive propagation phase control. By controlling the rotation angle between layers, not only can dynamically beam steering within each independent polarization channel be achieved, but the movement trajectory of the focused spot on the focal plane can also be further regulated. The experimental results obtained based on the probe-type near-field imaging system are in good agreement with the simulation results, with a measured maximum displacement difference of up to 4.23λ within the target rotation range and an average focal length of 8.8 mm. This low cost, multi-dimensional solution paves the way for compact integrated THz systems for high-precision applications such as real-time reconfigurable imaging.