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.

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.

A practical way to generate UV light is by converting more easily obtained infrared or visible laser beams into the UV light using nonlinear optics--harmonic generation processes in crystals.   This works well for producing light in nearly all of the UV A range (315 nm – 400 nm), the longest of the UV wavelengths.  There are several crystals that can do this job...