Sol–gel derived anti-reflective coatings for high fluence lasers

Sol–gel derived anti-reflective (AR) coatings, particularly those made by the Stöber silica process, have been used on glass and crystal optics in high power and energy laser systems for >30 years, employed on over 100,000 half-meter-scale optics. Sol–gel’s advantages include an appropriate refractive index, which provides high-efficiency anti-reflection, high chemical purity, which leads to high laser-damage resistance, and relatively low cost synthesis and coating processes. This chapter reviews the requirements and design for AR coatings, the sol–gel synthesis process (including reaction rates, surface chemistry, and particle-size and porosity controls), coating methods and post treatments, coating stability, and laser-damage performance.