Realizing Broadband Transparency via Manipulating the Hybrid Coupling Modes in Metasurfaces for High‐Efficiency Metalens

Abstract Metasurfaces with locally controlled phase discontinuity are promising for novel manipulations of the optical fields. However, the high insert loss at off‐resonance frequencies and narrow operation band of the resonant metasurface lead to the common low efficiency, obstructing it from practical applications. Here, it is shown that a broadband transparent metasurface, made of three‐layer complementary square ring resonator (CSRR) arrays, can be employed for high‐efficiency and broadband beam manipulation. The nonuniform metasurface can be optimized with high transmittance (above 90%) while maintaining full range (from 0 to 2π) phase modulation by adjusting the geometric parameters of the CSRR on the middle layer. The physical insight can be understood with a coupled oscillator model, it is found that the interlayer coupling constant is the key factor to realize phase modulation with high efficiency. A transmittance metalens with long focal depth in broadband is experimentally demonstrated as an example, the measured transmission efficiency is higher than 80%. The developed broadband wavefront engineering elements can be employed for high‐performance, miniaturized and superior environmental suitability sensing, imaging, and communication system.