Optical Coatings Prepared by the Sol-Gel Process

The sol-gel process is a versatile procedure used for the preparation of a large variety of oxide products, including optical coatings. Investigations into coatings for laser systems have been ongoing for nearly 30 years. Earlier work suffered from inconsistant damage threshold levels and expensive processing costs. Recent improvements, however, have resulted in the process being particularly successful in the preparation of quarterwave porous silica antireflection (AR) coatings for use in high power fusion laser systems. The laser damage thresholds are two to three times higher than coatings prepared by other methods. More recently, investigations into quarterwave, high-low index, multilayer, high-reflective (HR) coatings have resulted in products which, while not as superior as their AR equivalents, have compared favorably with competitive materials. The process is particularly suitable for large substrates and has the potential of economically producing the large number of optical coatings required for the next generation of fusion lasers.