Laser processing of insulator surfaces

Properties of insulators are strongly influenced by surface quality. Examples include anti-reflective or mirror coatings, surface waveguide lasers, high intensity laser damage resistance or chemical reactivity. Each of these properties can be degraded during polishing, coating deposition, diffusion or ion implantation of impurities, and by chemical reactions with the atmosphere. Laser beam processing is potentially beneficial in each of these cases. The laser energy may be confined to the surface layer by using strongly absorbed radiation, to give local heating which can anneal intrinsic defects, allow lattice restructuring to remove stress, induce crystalline regrowth or solid phase epitaxy. Removal of extended surface defects can enhance chemical and physical stability. By selection of optical absorption bands one can modify the penetration depth of the heat treatments. Pulsed laser heating has additional advantages in that thermodynamic conditions characteristic of high temperature can be frozen in place, as has been used to dissolve metallic colloids, without associated long range diffusion of the metal. Similarly, for ion implanted waveguide lasers, annealing is required within the guide region but damage at the guide boundary must be retained, which might be achieved by selection of wavelength and pulse duration. Other possibilities include domain poling, photorefractive and absorption grating patterning.