Oxyfluoride glasses of the compositions of 50SiO2•50PbF2•(5 - x)GdF3•xErF3 and 50SiO2•50PbF2•(5 - y)GdF3•0.1NdF3•yYbF3•0.1(Tb, Ho, Er or Tm)F3 in molar ratio (x =0.3 - 5 and y = 0 - 5) were developed. The oxyfluoride glasses were heat-treated at their first crystallization temperatures. Consequently, the crystals of -PbF2:(trivalent rare-earth ions) solid solutions uniformly precipitated in the scales of 15 20 nm in diameter in silicate glass matrices. These glass-ceramics were transparent to the naked eye. The glass-ceramics gave highly efficient upconversion luminescence based on the Tb3+, Ho3+, Er3+ or Tm3+ ion under 800 and/or 980 nm light excitation. These oxyfluoride glasses can be locally changed to glass-ceramics in the forms of dots, lines, letters, planes, etc. by irradiation of various lasers. The forms written by laser irradiation can be easily read from upconversion luminescence generated by the 800 and/or 980 nm laser illumination. Thus, the present oxyfluoride glasses can be applied to an optical memory device for specific information. Plates, fibers, thin films and coating-films in which the glass-powders are embedded in inorganic and/or organic polymers are considered as the shapes of oxyfluoride glasses that can be utilized as the device.