INFRARED TO VISIBLE UP-CONVERSION IN CS3YB2CL9-TM3+

Tm3+ doped Cs3Yb2Cl9 and Cs3Y2Cl9 was synthesized and single crystals were grown using the Bridgman technique. Absorption, upconversion lumi nescence and excitation spectra are presented as well as power- and co ncentration-dependent measurements. Under near-infrared (NIR) CW excit ation of the (2)F7/2 --> F-2(5/2) transition of Yb3+, Tm3+ doped Cs3Yb 2Cl9 exhibits intense NIR (H-3(4) --> H-3(6)), red (F-3(3) --> H-3(6)) , blue ((1)G(4) --> H-3(6) and D-1(2) --> F-3(4)) and near-UV (D-1(2) --> H-3(6)) upconversion luminescence. It is a stepwise energy transfe r with a very pronounced power and concentration dependence. The unusu al (compared to fluoride and oxide systems) red upconversion luminesce nce, assigned to a F-3(3) --> H-3(6) transition, is due to the low-ene rgy phonons (less than or equal to 280 cm(-1)) in this lattice. The po wer dependence and the dependence of the excitation spectra upon the d etection wavelength are reproduced by simple models.