Birefringent Glass‐Engraved Quasi‐Linear Nanograting Metasurface Based on Self‐Organizing Process for Large Aperture High Power Laser Applications

Abstract All‐glass metasurface “nanograting” structures that exhibit birefringence in the formed layer are reported. The key enabler of this work is ion beam processing at an angle sufficiently off‐normal incidence, inducing self‐assembly of a deposited metal layer into quasi‐linear metallic features that can function as an etching mask. As a result, a fused silica metasurface, monolithic to the underlying substrate, is demonstrated at 375 nm wavelength to exhibit a phase delay angle of 30° between the principal axes. The capability of an angled etch mask replenishment process is also demonstrated for achieving deeper etch depth and for increasing the grating period, another first – to the best of the knowledge. This is the first display of a technology capable of fabricating glass‐engraved near‐linear grating structure with a feature‐to‐feature period as small as 118.6 nm. Furthermore, this technology has the potential to generate grating‐like structures with periods as small as 12.4 nm, as demonstrated here with reactive ion beam processing assisted mask assembly. These structures are shown to have reflectivity < 0.4% across the wavelength band 350 nm – 1000 nm. Such a technology can enable laser‐durable grating structures for the deep‐UV and even down to soft X‐ray wavelengths.