Uncoated LBO crystal surfaces can survive fluences exceeding 95 J/cm² at 355 nm, but conventional AR coatings fail at 20–30 J/cm². ARSS technology addresses this by replacing deposited thin films with sub-wavelength surface structures that create a gradient refractive index with no discrete interfaces to crack or delaminate. GAMDAN Optics is working to bring this approach to high-power frequency conversion systems.

The details of a coating design involve the thickness and material choice for each coating layer.  This affects the optical field intensity distribution within the coating, and that affects the laser induced damage threshold (LiDT).  The choice of coating materials also affects the thermal expansion mismatch between the coating and the substrate, a factor that affects coating adhesion and coating cracking or crazing.

This article will concentrate on coatings applied by vacuum deposition, which gives durable reliable coatings. There are other techniques for reducing surface reflectivity such as sol-gel coatings or nano-structured surfaces.