We report on the use of $800\mathrm{nm}$ , $250\mathrm{kHz}$ femtosecond laser pulses to precipitate ${\mathrm{Er}}^{3+}$ -doped $\mathrm{Ca}{\mathrm{F}}_2$ crystals inside oxyfluoride glass, which was confirmed with x-ray diffraction analysis. Confocal upconversion luminescence spectra show that the precipitated crystals have greatly enhanced upconversion luminescence intensity in comparison with unmodified glass. We demonstrate the possibility of three-dimensional optical data storage in the glass by the use of the confocal upconversion luminescence imaging.