Wavelength-tailorable infrared image processing via a metal-silicon hybrid nanostack.

Optical imaging processing is an attractive technology for extracting essential information from target objects without any digital computations. Although various nanophotonic devices have been studied for versatile image processing, their transfer function typically relies on extensive optimizations, thus increasing computational costs when faced with arbitrary wavelength requirements. Here, a metal-silicon hybrid nanostack is demonstrated for wavelength-tailorable optical image processing in the near-infrared range. By employing the cavity-induced wavelength/angle-sensitive property, the nanostack with five-layered nanofilms directly manipulates the transmittance of light in the wavevector domain, and performs edge-enhanced imaging and bright-field imaging in different wavelength channels. Moreover, due to the dual Fabry-Perot cavity architecture, the operating wavelength of the nanostack can be effectively and continuously tuned from 850 nm to 1250 nm by merely scaling the silicon layer thickness, beyond re-optimization strategies. The proposed nanostack with a simple architecture is easy to fabricate and integrate into compact optical imaging systems and suggests practical applications in machine vision, optical computing, and intelligent image recognition.