Propagation characteristics of the blocked terahertz ring-Airy beam generated by all-silicon metasurface

Based on the all-silicon metasurface, we study the propagation characteristics of the abruptly autofocusing terahertz (THz) ring-Airy beam when its primary ring is blocked. Identical rectangular silicon pillars with meticulously designed rotation angles are arranged on a silicon substrate to shape the incident linearly polarized plane wave into a cross-polarized blocked ring-Airy beam. The transmission efficiency of the metasurface can be up to 77.57% since a polarization-independent square silicon pillar array is patterned at the other side of the substrate to suppress the reflection loss. Compared to the ring-Airy beam, the abruptly autofocusing property of the blocked ring-Airy beam is promoted since the intensity contrast at the focus is greatly enhanced. In addition, the focus of the blocked ring-Airy beam is smaller and the focus position of it slightly moves forward. The principle feasibility of the metasurface and influences of imperfections on the propagation characteristics of the generated blocked ring-Airy beam are also discussed. Our study is expected to be of great significance for applying THz waves in manipulation of particles and biomedicine.