论文标题
非本地宽视野金属的厚度
Thickness bound for nonlocal wide-field-of-view metalenses
论文作者
论文摘要
金属镜 - 由光学跨面制成的扁平镜头 - 有望使更薄，更便宜，更好的成像系统。实现足够的角度视野（FOV）对该目标至关重要，需要量身定制的入射角依赖性响应。在这里，我们表明，达到所需的广角响应与降低设备的厚度之间存在一个内在的权衡。它源自空间和角度之间的傅立叶变换二元性。可以写下描述所需角度依赖性响应的传输矩阵，将其转换为空间基础，在该空间基础上，可以通过横向扩展来量化其非局部性程度，并根据所需的横向扩散确定最小的设备厚度。这种方法是一般的。当应用于宽大镜头时，它可以预测最小厚度，这是FOV，透镜直径和数值光圈的函数。绑定是紧密的，因为一些反设计的多层元面积可以接近我们发现的最小厚度。这项工作为设计非本地元信息设计提供了指导，为建立界限提供了一个新框架，并揭示了角度多样性与多通道系统中的空间足迹之间的关系。
Metalenses -- flat lenses made with optical metasurfaces -- promise to enable thinner, cheaper, and better imaging systems. Achieving a sufficient angular field of view (FOV) is crucial toward that goal and requires a tailored incident-angle-dependent response. Here, we show that there is an intrinsic trade-off between achieving a desired broad-angle response and reducing the thickness of the device. It originates from the Fourier transform duality between space and angle. One can write down the transmission matrix describing the desired angle-dependent response, convert it to the spatial basis where its degree of nonlocality can be quantified through a lateral spreading, and determine the minimal device thickness based on such a required lateral spreading. This approach is general. When applied to wide-FOV lenses, it predicts the minimal thickness as a function of the FOV, lens diameter, and numerical aperture. The bound is tight, as some inverse-designed multi-layer metasurfaces can approach the minimal thickness we found. This work offers guidance for the design of nonlocal metasurfaces, proposes a new framework for establishing bounds, and reveals the relation between angular diversity and spatial footprint in multi-channel systems.
