Mechanically and thermally stable thin sheets of broadband antireflection surfaces fabricated by femtosecond lasers

Abstract

Fabrication of extreme black surfaces using femtosecond laser micromachining is demonstrated. Mechanical and thermal stability are important parameters that limit the lifetime performance of anti-reflective surfaces in optical instruments. We have fabricated nanostructured omnidirectional anti-reflective surfaces on a light-weight, thin stainless-steel sheets of thickness 50 and 100 μm. This work reports less than 0.5% reflectivity for a wide range of wavelength from UV to NIR (400 to 2500 nm) and with the wide acceptance of incidence angles (±60°). Cross-sectional thickness variations and mechanical strengths of these laser irradiated sheets are tested by using the FESEM and Micro Vickers hardness studies, respectively. We demonstrated thermal stability up to 300 °C temperature and much superior mechanical strength than chemically coated surfaces for broadband applications. These ultra-black SS thin sheets have potential applications in suppressing stray light in many optical and optoelectronic devices, low light imaging sensors, solar cells, satellite-based optical payloads, etc.