Advances in spatial analog optical computing devices

Abstract

Spatial analog optical computing devices possess the capability of high-throughput, real-time and low-energy information processing. Optical metamaterials, which are ultracompact in structure and possess powerful ability to control the light, can be utilized to establish miniatured and integrated spatial analog optical computing devices. The methods of designing the spatial analog optical computing devices could be mainly classified as two kinds—4F system method and Green’s function method. The 4F system method requires two Fourier transform lenses and a spatial frequency filter, where the actual computing procedure is performed in the spatial domain. The 4F system is usually bulky and complicated. The Green’s function method directly leverages the nonlocal response of the carefully tailored optical materials to implement analog computing procedure in the spatial frequency domain and its structure is compact without extra Fourier transform components. Research advances in spatial analog optical computing devices by using these two methods for the last few years are introduced in this paper. These researches could be classified as differentiators, integrators, equation solvers and spatial frequency filters according to the standard of computing functions. The approaches to designing these devices are further demonstrated. Then, computing devices which could realize spatial analog first-order difference by use of the spin-orbit interaction proposed recently are introduced. Finally, application fields and study prospects of spatial analog optical computing devices are discussed and summarized.