Broadband High-Efficiency Nonreciprocal Transmission Enabled by Silicon/Vanadium Dioxide Catenary Metasurfaces

Abstract

Nonreciprocal transmission based on nonlinear optical materials has attracted considerable attention for eliminating the need for complex and bulky external bias systems and shows great potential for high-intensity laser protection. Strongly resonant structures are commonly used to achieve lower laser operating power and higher efficiency. However, this approach typically compromises other critical performance metrics, such as protection power range, maximum operating power, bandwidth, and angular range. Here, a novel strategy is proposed using weakly resonant structures to realize nonreciprocity while preserving high performance across these metrics. This achievement stems from the large out-of-plane refractive index asymmetry in the Si/VO₂ catenary structure, enabling robust nonreciprocal transmission with high efficiency across a broad bandwidth (8–11.5 µm) and angular range (>75°) theoretically. This design also shows a higher operating power ceiling and extends the existing tunable nonreciprocal range by an order of magnitude. Experiments validate the tunable nonreciprocal range at 10.6 µm wavelength. Protection capabilities are significantly enhanced through wavefront modulation, offering rapid and effective protection from below the phase transition to above the damage threshold. This work presents a novel paradigm for robust nonreciprocal metasurfaces, with considerable potential for applications in remote sensing, environmental monitoring, biomedicine, and industrial manufacturing.