Broadband, Transmissive, and Cascadable Terahertz Programmable Metasurface

Programmable metasurfaces have emerged as versatile tools for optical information processing across a wide range of frequencies. The existing designs in the terahertz band primarily work in reflective modes with a narrow bandwidth, leading to a complex optical path and challenges in integrating with other optical components. Here, we proposed a transmissive programmable metasurface based on a vanadium dioxide film transferred onto an ultrathin substrate and demonstrated its capability for matrix operations in a dual-layer cascaded configuration. The metasurface consists of 8 × 8 independently electrically addressable pixels, achieving an insertion loss of less than 3 dB in the ON state at frequencies below 1 THz. It exhibits a modulation depth exceeding 75% from 1.01 to 1.80 THz and greater than 50% in the OFF state across 0.51-1.80 THz, corresponding to a modulation bandwidth of up to 111%. The device can also operate under bent conditions. The proposed transmissive programmable metasurface, with its optically thin thickness, ease of stacking, and efficient transmission, presents a promising pathway for the realization of compact, high-efficiency, and multifunctional optical systems.