Low Reflectance all‐Glass Metasurface Lenses Based on Laser Self‐generated Nanoparticles

ABSTRACT Optical metasurfaces, comprised of subwavelength nanostructures, hold a great promise to high‐power laser optics but also a limited pertinence due to their currently limited aperture size, throughput and durability. Here, an alternative approach is presented, reliant on laser‐controlled self‐organizing mask formation followed by ion etching which results in an all‐fused‐silica‐glass metasurface, for enhanced durability. Two 1 mm diameter optical elements (an axicon lens and a shadower) are fabricated and their optical performance is validated at 532 nm wavelength with an extremely low broadband reflection (<0.15%)—a result of their elongated and tapered metasurface elements shape. The self‐organizing working principle enables producing large amounts of nano‐elements at‐once, thus a path for aperture scaleup. It also enables generation of sub‐100 nm nanoelements, thus a path to short wavelengths operation. Two key advancements are presented: a laser scan with in situ mask transmission feedback enables patterning the etching mask to a prescribed nanoparticle distribution with a gradually varying mask structure, and a crafted beyond‐mask‐erosion‐point etching of the mask enables increasing the metasurface phase difference to at least π, while keeping extremely low reflection across it.