Optical quality improvement of rare-earth doped silica layers by CO2 laser irradiation

► CO2 laser heating is used to treat structural defects in Yb/Al codoped silica layers. ► Micro-scale voids are removed by diffusion. ► Crystallites are analyzed by micro-Raman and shown to undergo complete amorphization. ► Surface roughness is reduced from 165 nm to 15 nm via surface-tension-driven mass-flow. ► Optical transmittance is increased from less than 20% to more than 95% at 633 nm over 1 cm.