ROOM-TEMPERATURE BLUE UP-CONVERTED LUMINESCENCE VIA PHOTON AVALANCHE PUMPING IN CS2NAGDCL6-TM3+

Experimental results are presented to show that the intense, blue upco nverted luminescence observed from Cs2NaGdCl6 doped with 6, 10 and 15 at.% Tm3+, when excited by a cw laser near 650 nm at room temperature, is due to a photon avalanche process. A slow rise of the upconverted blue-emission intensity, over several seconds, takes place near the th reshold power level. Emission is not only observed from the (1)G(4) te rm manifold, but also from D-1(2). The well-resolved upconversion exci tation spectrum indicates clearly that excited-state absorption to (1) G(4) takes place from the F-3(4) multiplet term of Tm3+.