Wavelength‐selective coatings on glass with high hardness and damage resistance

Abstract

Wavelength‐selective coatings are broadly applied across diverse industries such as solar energy management, infrared sensing, telecommunications, laser optics, and eye‐protective lenses. These coatings have historically not been optimized for hardness or mechanical durability and typically suffer from higher susceptibility to scratch and damage events than uncoated glass. In this work, we describe a family of wavelength‐selective coatings with hardness and scratch resistance that are significantly higher than the chemically strengthened glass substrates on which the coatings are fabricated. The coatings are made using industrially scalable reactive sputtering methods. Wavelength‐selective coatings are fabricated with nanoindentation hardness as high as 16–20 GPa over indentation depths ranging from 200 to 800 nm, as well as excellent durability in aggressive scratch testing. Tunable visible to near‐infrared wavelength selectivity ratios (reflectance of stopband: reflectance of passband) as high as 7:1 are achieved. The feasibility of narrowband hard coating design is also demonstrated, with visible narrowband transmission having a peak FWHM of ~8 nm (~1.6%). A unique “buried layers” hard coating design strategy is shown to deliver particularly excellent hardness profiles. These designs can be tailored for a variety of different wavelengths and selectivity ratios, enabling new uses of wavelength‐selective optics in mechanically demanding applications.