非对称成像：互易性界限与表现
Asymmetric imaging: Reciprocity bounds and manifestations
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中文总结 AI 辅助
本研究提出非对称成像的一般理论，推导出互易系统中单向性的基本界限，并展示了折射系统与超表面双合透镜两种实现，为跨平台非对称成像提供基准与设计原则。
中文摘要 AI 辅助
最近利用衍射多层结构的单向成像演示，将类似于光学隔离的概念引入了成像领域，然而这种非对称性的基本极限仍然未知。在此，我们发展了线性、无源、互易光学系统中非对称成像的一般理论，并推导出可实现单向性的基本界限。互易性要求前向和后向传输算子具有相同的奇异值，这是光学扩展量相等性的波动光学类比，其简单推论是：完美的非对称性仅对 $M \leq N/2$ 个正交物体图案的集合可实现，其中 $N$ 是可用的物体/图像模式数；对于 $M > N/2$，平均功率非对称性受 $(N-M)/M$ 限制。在这一结果的指导下，我们提出了两种互补的实现方案：由体透镜和光阑构成的折射成像系统达到半占据极限，以及一个直径1厘米的全硅超表面双合透镜，在4微米波长处表现出非对称聚焦，同时完全符合洛伦兹互易性。我们通过直接激光写入制造了该双合透镜，并实验证明了其聚焦非对称性。通过建立与机制无关的界限，我们的结果为跨平台非对称成像提供了基准和设计原则，对国防、监视和安全通信具有重要意义。
英文摘要
Recent demonstrations of unidirectional imaging using diffractive multilayers have brought a concept akin to optical isolation to imaging, yet the fundamental limits of such asymmetry have remained unknown. Here we develop a general theory of asymmetric imaging in linear, passive, reciprocal optical systems and derive a fundamental bound on the achievable unidirectionality. Reciprocity requires the forward and reverse transmission operators to have identical singular values, a wave-optical analogue of étendue equality, with a simple consequence: perfect asymmetry is attainable only for sets of $M \leq N/2$ orthogonal object patterns, where $N$ is the number of available object/image modes; for $M > N/2$, the average power asymmetry is bounded by $(N-M)/M$. Guided by this result, we present two complementary realizations: refractive imaging systems formed by bulk lenses and stops that attain the half-occupation limit, and a 1 cm-diameter all-silicon metasurface doublet that exhibits asymmetric focusing at 4 $μ$m while fully complying with Lorentz reciprocity. We fabricate the doublet by direct laser writing and experimentally demonstrate its focusing asymmetry. By establishing mechanism-independent limits, our results provide a benchmark and design principle for asymmetric imaging across platforms, with implications for defense, surveillance and secure communications.
发表机构
- University of Washington（华盛顿大学）
- University of Colorado, Boulder（科罗拉多大学博尔德分校）
- City University of New York（纽约市立大学）
- Yale University（耶鲁大学）
机构由 AI 辅助整理，请以论文原文为准。
