All-optical image tracking based on the silicon metasurface

Abstract

Effective control of electromagnetic radiation in the optical range is one of the key challenges in modern photonics. Recently, there has been a lot of research in the field of metamaterials – artificial subwavelength structures with specific optical properties defined by their geometry. It has been shown that such structures offer wide opportunities to manipulate light at the nanoscale. However, the fabrication of such structures is a technically challenging task. On the other hand, their 2d analogous - metasurfaces - based mainly on dielectric and semiconductor materials, are of greater interest due to the CMOS-compatibility and lower energy losses compared to their plasmonic counterparts. Recent research has shown the ability of metasurfaces to control the phase and amplitude of light waves on-demand with high efficiency, which paves the way for the creation of ultrathin elements such as metalenses, holograms and beam-shapers. They also can be used for optical analogue computing and processing of optical signals in real-time (such as differentiation, integration or convolution). These numerical studies allowed to demonstrate the result of the convolution of two images and obtain bright correlation peaks in the regions where the reference image was located in the analyzed one. Based on the achieved numerical results the sample of the silicon metasurface on a glass substrate was made by electron beam lithography and reactive ion etching techniques. Using this sample, a set of experimental tests was carried out to validate our numerical model. Achieved results can pave the way for the realization of new devices for analogue optical image processing based on CMOS-compatible metasurfaces.