Enriching Metasurface Functionalities by Fully Employing the Inter‐Meta‐Atom Degrees of Freedom for Double‐Key‐Secured Encryption

Creating new functionalities has long been the driving impetus for the development of metasurfaces and meta‐devices. This has routinely been achieved by exploiting the intrinsic degrees of freedom (DoFs) of their building blocks—meta‐atoms, such as searching for new materials or increasing geometric variations. However, these approaches are ultimately bottlenecked by the limited species of natural materials, and often incur additional design or fabrication difficulties. In this work, the authors resort to the relative and absolute structural DoFs at the inter‐meta‐atom (IMA) level to circumvent the above‐mentioned limitations. Eventually, a novel double‐key‐secured encryption system with increased image storage capacity approaching the theoretical limit is successfully devised by fully employing all the IMA DoFs. The generic design approach, which provides a new means to enrich the metasurface functionalities by expanding the capacity of meta‐devices, can be readily adapted in the design of other nanophotonic systems.