High‐quality flat optical elements require efficient light deflection to large angles and over a wide wavelength spectrum. Although phase gradient metasurfaces achieve this by continuously adding phase shifts in the range of 0–2π to the electric field with subwavelength‐sized scatterers, their performance is limited by the spatial resolution of phase modulation at the interface. Here, a new class of metasurfaces is introduced, where the phase shifts cover less than the full 0–2π range, offering significant advantages. This approach allows the realization of metasurfaces with more compact and less mutually‐interacting scatterers, and thus more precise phase modulation, and advances the performance limits of metasurfaces to domains significantly beyond those of the full coverage phase gradient approach. Applying this concept to both plasmonic and dielectric surfaces, large phase gradients resulting in high‐numerical‐aperture immersion metalenses (NA = 1.4) with near diffraction‐limited resolution (≈0.32λ) at visible wavelengths are demonstrated. This concept enables added functionalities such as broadband performance and wavelength de‐multiplexing on a single layer, surpassing the theoretical cross‐polarization transmission efficiency limit for single‐layer plasmonic metasurfaces, and yields 67% efficiency for dielectric metasurfaces. This work paves the way toward realizing high‐resolution flat optical elements and efficient plasmonic metadevices.

中文翻译：

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基于光相位的部分控制的高效，极限数值孔径超表面

高质量的平面光学元件需要在较大的角度和宽的波长光谱范围内进行有效的光偏转。尽管相位梯度超表面通过使用亚波长大小的散射体向电场连续添加0–2π范围内的相移来实现此目的，但它们的性能受到界面处相位调制的空间分辨率的限制。在这里，引入了一类新的超表面，其中相移的覆盖范围小于整个0–2π，具有明显的优势。这种方法可以实现具有更紧凑且相互影响较小的散射体的超颖表面，从而实现更精确的相位调制，并使超颖表面的性能极限大大超越了全覆盖相梯度方法。将该概念应用于等离子和介电表面，证明了大的相位梯度导致可见光波长下具有接近衍射极限分辨率（≈0.32λ）的高数值孔径沉浸金属感（NA = 1.4）。该概念可实现单层宽带性能和波长解复用等附加功能，从而超越了单层等离子体超颖表面的理论交叉极化传输效率极限，并为电介质超颖表面产生了67％的效率。这项工作为实现高分辨率平面光学元件和高效的等离子元设备铺平了道路。该概念可实现单层宽带性能和波长解复用等附加功能，从而超越了单层等离子体超颖表面的理论交叉极化传输效率极限，并为电介质超颖表面产生了67％的效率。这项工作为实现高分辨率平面光学元件和高效的等离子元设备铺平了道路。该概念可实现单层宽带性能和波长解复用等附加功能，从而超越了单层等离子体超颖表面的理论交叉极化传输效率极限，并为电介质超颖表面产生了67％的效率。这项工作为实现高分辨率平面光学元件和高效的等离子元设备铺平了道路。