Ultraviolet and white photon avalanche upconversion in Ho3+-doped nanophase glass ceramics

Ho3+-doped fluoride nanophase glass ceramics have been synthesized from silica-based oxyfluoride glass. An intense white emission light is observed by the naked eye under near infrared excitation at 750nm. This visible upconversion is due to three strong emission bands in the primary color components, red, green, and blue. Besides, ultraviolet signals are also recorded upon the same excitation wavelength. The excitation mechanism of both the ultraviolet and the visible emissions is a photon avalanche process with a relatively low pump power threshold at about 20mW. The total upconverted emission intensity has been estimated to increase by about a factor of 20 in the glass ceramic compared to the precursor glass, in which an avalanche type mechanism is not generated.