Upconversion glass-ceramic devices of individual emission of red, green, and blue and their applications

Abstract

When rare earth-doped oxyfluoride glasses are heat-treated at the first crystallization temperatures, the glasses turn into glass-ceramics in which rare earth-containing nanocrystals uniformly precipitate in the glass matrices. These glass-ceramics are transparent to the naked eye as well no heat-treated glasses. Since rare earth ions exist as solid-solution ions in the precipitated fluoride crystals with low phonon energies, these glass-ceramics exhibit highly efficient up-conversion luminescence by laser light excitation. In the present work, rare earth-doped oxyfluoride glass-ceramics in the SiO2-PbF2-HoF3-YbF3-GdF3, and SiO2-PbF2-TmF3-YbF3-GdF3 systems were developed. Under 980nm LD excitation the respective glass-ceramics gave selectively red-, green-, and blue-upconversion luminescence with high efficiency. Emission wavelengths in the center of gravity are 666, 543, and 479 nm, respectively. Except for these selective emissions, however, other emissions at different wavelengths are also observed, though extremely weak. Removal of these extra emissions was possible by using appropriate filter-glasses, presenting the up-conversion devices of individual emission of red (R), green (G), and blue (B). On the other hand, laminas of the mixtures of resin and the glass-ceramic powders exhibited extremely high enhancement of upconversion emission intensities. The developed upconversion glass-ceramics in which RGD emissions are independently available by 980 nm laser irradiation offer a variety of applications. Some of the expected utilization as optics devices is proposed.