Laser patterning and enhanced red photoluminescence of Er3+/Yb3+ co-doped CaF2 crystal dots and lines in oxyfluoride glasses

The laser-induced crystallization method is applied to Er3+/Yb3+ co-doped oxyfluoride glasses, and dots and lines consisting of CaF2 crystals are patterned on the glass surface in order to clarify whether co-doping of different rare-earth ions (Er3+ and Yb3+) is possible even into laser-patterned fluoride crystals. The morphology (bump's height and width) of dots and lines formed by laser (continuous-wave Yb:YVO4 fiber laser with a wavelength of 1080 nm) irradiations is examined from confocal scanning laser microscope observations. It is found that the intensity of photoluminescence peaks corresponding to the 4F9/2 → 4I15/2 transition (red) of Er3+ ions in the laser-patterned CaF2 crystals in Er3+/Yb3+ co-doped glasses are enhanced largely compared with laser-patterned CaF2 crystals in only Er3+-doped glasses, suggesting that both Er3+ and Yb3+ ions might be incorporated into CaF2 crystals. The present study proposes that the laser irradiation technique is extremely effective in crystallizing rare-earth doped fluoride crystals in oxyfluoride glasses.