Why optics needs thickness

This study shows why and when optical systems need thickness as well as width or area. Wave diffraction explains the fundamental need for area or diameter of a lens or aperture to achieve some resolution or number of pixels in microscopes and cameras. This work demonstrates that if we know what the optics is to do, even before design, we can also deduce the minimum required thickness. This limit comes from diffraction combined with a concept called overlapping nonlocality C that can be deduced rigorously from just the mathematical description of what the device is to do. C expresses how much the input regions for different output regions overlap. This limit applies broadly to optics, from cameras to metasurfaces, and to wave systems generally. Description Determining limits on optical thickness The functionality and performance of optical components has largely been limited by the optical materials available. Recent developments in fabrication and optical component design now widen what can be achieved. In particular, flat optics or metasurfaces can be designed with the functionality of bulk optical components but with their thickness shrunk to just several hundred nanometers. Miller now presents a theoretical study to determine what the minimum thickness can be for a specific optical function (see the Perspective by Monticone). The approach is general and should provide bounds on the minimum size of other wave systems, including radio and acoustic systems. —ISO Wave physics predicts a minimum size for optical components dependent on their function.