Morphology and photoluminescence properties of Er3+-doped CaF2 nanocrystals patterned by laser irradiation in oxyfluoride glasses

Lines with Er3+-doped CaF2 nanocrystals were patterned by laser irradiations in aluminoborosilicate-based oxyfluoride glasses. The morphology and dispersion state of CaF2 nanocrystals were examined from transmission electron microscope (TEM) observations combined with focused ion beam sample preparations. The size of CaF2 nanocrystals present in the region close to the center of lines was larger than that in the region close to the edge of lines. Micro-photoluminescence (PL) spectra for the line part showed clear emissions corresponding to the f–f transitions of Er3+ ions, and the correlation between the morphology and dispersion state of CaF2 nanocrystals and PL properties (intensity and degree of the Stark splitting) of Er3+ ions incorporated into in CaF2 nanocrystals was clarified. The formation mechanism of CaF2 nanocrystals in the laser irradiated part was discussed from the temperature distribution model.