Lanthanide-doped glasses as frequency-converter for high-power LED applications

Abstract Lanthanide-doped borate glasses represent an attractive alternative as frequency-converter for white-light generation. The CIE colour coordinates of Tm 3 + , Tb 3 + , and Eu 3 + double- and triple-doped glasses can be tuned over a broad spectral range by varying the lanthanide doping concentrations and ratios accordingly. In addition, double- and triple-doping allow for a change in colour coordinates by using different excitation wavelengths. To overcome the problem of poor optical absorption of the doped lanthanide ions and to increase the optical path length for the excitation light, the as-made glass is successfully processed to a glass ceramic. The amount of crystallites grown in the glass is controlled by appropriate choice of annealing time and temperature. The glass ceramics do not only offer enhanced optical properties, but also improved thermal properties. The thermal diffusivity of the glass ceramic is one order of magnitude higher than that of the glass.