RED LASER-INDUCED UP-CONVERSION LUMINESCENCE IN ER-DOPED CALCIUM ALUMINUM GERMANATE GARNET

In this work, we have studied the spectroscopic and dynamic properties of the green (S-4(3/2) --> 4I(15/2)) and blue (P-2(3/2) --> I-4(11/2) ) upconversions for a series of Er3+ doped Ca3Al2Ge3O12, induced by a red tunable laser excitation. The green emission is due to either an e nergy transfer involving two ions excited in the I-4(11/2) multiplet o r an excited state absorption from the I-4(13/2) level, depending on w hether the laser excitation wavelength is tuned on I-4(15/2) --> F-4(9 /2) or I-4(13/2) --> F-4(5/2). The blue emission mainly results from a three-step absorption process through the I-4(13/2) and S-4(3/2) mult iplets. The temperature and concentration effects have been analyzed f or the green and blue upconversions. (C) 1997 American Institute of Ph ysics.