Mid-Wavelength Infra-Red Metalenses and Large-area All-Silicon Meta-optics

Abstract

Mid-Wavelength Infra-Red (MWIR) meta-optics are an interesting research subject since these fabricated optics have uses in many fields and are at the core of some new technologies. Specifically, all silicon meta-optics that are fabricated on a thin 300 micron wafer cut thin and go through an electrochemical planarization from a 100mm diameter Silicon (100) crystal allow for compact and lightweight lenses. These properties, namely lightness, compactness, and high durability allow for uses in small unmanned aerial vehicles (UAVs), surveillance drones, infra-red cameras as well as wearable night vision goggles. Future applications can include smartphones, AR/VR, wearables, automotive, robotics, IoT platforms, as meta-lenses are optimal for presence detection, face identification, gesture recognition, eye-tracking, driver monitoring systems, and medical instrumentation. [1] In the core principle of the operation of meta-optic are the meta-atoms. The flat surface of the silicon wafer is patterned with structures called ‘nanopillars’ that are smaller than the wavelength of light that they are designed to manipulate. The pillars are usually made square so that their width and length is the same. The distance between the pillars or how far apart they are is usually constant and is engineered so that they are effective at lensing the light in the specific optical regime (wavelength). In this work the meta-optics are designed to operate in MWIR regime, which is 3 to 5 um peak to peak wavelength thus the spacing between the pillars is 1.6 um between the 400nm pillars or 400nm between 1.6nm pillars necessary to pattern a hyperboloid meta-lens. The minimum feature size was 400 nm, which was pushing the resolution limit of our direct laser write system at Washington Nanofabrication Facility (WNF).