Broadband polarization conversion metasurface for beam deflection with switchable characteristics

We present a dynamically switchable polarization conversion metasurface (PCM) integrated with an electromechanical actuator (EMA) that enabled the switching of states for the reflected wavefront of circularly polarized waves in the terahertz (THz) spectrum. The unit cell of the proposed PCM was composed of double L-shaped Au structures covering a dielectric layer suspended atop a bottom reflective mirror layer. The PCM showed a broad polarization conversion band ranging from 0.74 THz to 1.64 THz with a polarization conversion ratio >90% for incident linear polarized (LP) and circular polarized (CP) waves. Within this broadband, the full 2π phase shifts of the reflected orthogonal CP wave could be obtained by rotating the orientation angle of the PCM unit cell spanning a wide frequency range. The anomalous reflection effect of PCM was simulated and discussed to validate the performance of the proposed switchable coding metasurface based on Pancharatnam–Berry phase theory and the generalized Snell's law. In particular, the reflection efficiency could be tuned dynamically by transforming the movable configuration. The proposed PCM had significant potential for applications in imaging and communication systems, which opens new avenues for the development of multifunctional devices that can modulate THz wavefronts.