UP-CONVERSION LUMINESCENCE IN ER3-DOPED RBGD2CL7 AND RBGD2BR7()

Er3+-doped RbGd2Cl7 and RbGd2Br7 have been synthesized and grown as cr ystals using the Bridgman technique. Crystal absorption, upconversion luminescence, and Raman spectra are presented. Efficient infrared to v isible upconversion is observed in both compounds at all temperatures between 10 and 295 K. Under I-4(9/2) excitation around 800 nm both com pounds show similar upconversion spectra, whereas their behavior is di stinctly different for 4I(11/2) excitation around 980 nm. The green li ght of the chloride originates from S-4(3/2) luminescence, whereas the bromide has a pure F-4(7/2) luminescence in the blue. This is due to the difference in the highest-energy vibration which is 264 and 180 cm (-1) for the chloride and bromide, respectively. Estimates of radiativ e and nonradiative rate constants are made for the various processes d epopulating the F-4(7/2) state. Measured oscillator strengths of f-f t ransitions are compared with those determined from a Judd-Ofelt calcul ation. It is found that the F-4(7/2) --> I-4(15/2) is a potential lase r transition in bromide lattices.