Spatially selected synthesis of LaF3 and Er3+-doped CaF2 crystals in oxyfluoride glasses by laser-induced crystallization

Oxyfluoride glasses with a small amount of NiO are prepared using a conventional melt quenching technique, and the spatially selected crystallization of LaF3 and CaF2 crystals is induced on the glass surface by irradiations of continuous wave lasers with a wavelength of λ=1064 or 1080 nm. Dots and lines including LaF3 crystals are patterned by heat-assisted (300 deg. C) laser irradiations (λ=1064 nm) with a power of P=1 W and an irradiation time of 10 s for dots and a scanning speed of S=5 μm/s for lines. Lines consisting of CaF2 crystals are also patterned in an ErF3-doped oxyfluoride glass by laser irradiations (λ=1080 nm) with a power of P=1.7 W and a scanning speed of S=2 μm/s, and the incorporation of Er3+ ions into CaF2 crystals is confirmed from micro-photoluminescence spectrum measurements. It is proposed that the lines patterned by laser irradiations in this study are consisted of the composite of LaF3 or CaF2 nanocrystals and SiO2-based oxide glassy phase. It is demonstrated that a combination of Ni2+-dopings and laser irradiations is effective in spatially selected local crystallizations of fluorides in oxyfluoride glasses. - Graphical abstract: This figure shows the polarization optical and confocal scanning laser micrographs for lines obtained by laser irradiations with a laser power of P=1.7 W and a scanning speed of S=2 μm/s in an oxyfluoride glass. It is proposed that the line consists of the composite of CaF2 nanocrystals and oxide glassy phase. This is the first demonstration on the patterning of fluoride crystals in glass by laser irradiations