Extended depth of focus (EDOF) lenses are important for various applications in computational imaging and microscopy. In addition to enabling novel functionalities, EDOF lenses can alleviate the need for stringent alignment requirements for imaging systems. Existing designs, however, are often inefficient or produce an asymmetric point spread function (PSF) that blurs images. Inverse design of nanophotonics, including metasurfaces, has generated strong interest in recent years owing to its potential for generating exotic and innovative optical elements, which are generally difficult to design based on intuition alone. Using adjoint optimization-based inverse electromagnetic design, in this paper, we designed a cylindrical metasurface lens operating at ∼625 nm with a depth of focus exceeding that of an ordinary lens. We validated our design by nanofabrication and optical characterization of silicon nitride metasurface lenses (with a lateral dimension of 66.66 μm) with three different focal lengths (66.66, 100, and 133.33 μm). The focusing efficiencies of the fabricated extended depth of focus metasurface lenses are similar to those of traditional metalenses.

中文翻译：

---

具有扩展景深的逆设计Metalense

扩展景深（EDOF）镜头对于计算成像和显微镜的各种应用至关重要。除了实现新颖的功能外，EDOF镜头还可以减轻对成像系统的严格对准要求。但是，现有设计通常效率低下，或者会产生使图像模糊的不对称点扩散函数（PSF）。纳米光子学，包括超颖表面的逆向设计，由于其具有产生奇异和创新光学元件的潜力，近年来引起了人们极大的兴趣，而这些光学元件通常仅凭直觉很难设计。本文采用基于伴随优化的逆电磁设计，设计了一种在〜625 nm下工作的圆柱超表面透镜，其焦深超过了普通透镜。我们通过纳米制造和具有三种不同焦距（66.66、100和133.33μm）的氮化硅超表面透镜（横向尺寸为66.66μm）对我们的设计进行了验证。所制造的扩展焦深超表面透镜的聚焦效率与传统的metalenses相似。