High brightness blue and green light sources pumped with a 980 nm emitting laser diode

Abstract
Efficient frequency upconversion from 980 nm infrared light to 480 nm wavelength blue emission has been observed in Tm3+-activated, Yb3+-sensitized fluoride glass. Similar upconversion to green emission has been obtained with higher efficiency in Er3+-containing luminescent materials. The conversion efficiencies have been markedly improved when the luminescent material small in size is contained in a reflective cavity. The improvement effect is pronounced when transparent luminescent material is adopted. Processes leading to the generation of visible emission have been examined and criteria for optimizing the upconversion efficiency are presented.