SITE SELECTION AND UP-CONVERSION STUDIES IN ERBIUM AND YTTERBIUM DOPED CSCDBR3

A detailed study of absorption and fluorescence lines of transitions between excited state S-4(3/2) and ground state I-4(15/2) has been carried out in several doped and codoped samples. Polarized absorption confirmed the C3v site symmetry of Er3+. Using laser excitation in the F-4(7/2) level, three kinds of Er3+ sites have been observed and attributed to Er3+-vacancy-Er3+, Er3+-Er3+-vacancy dimers and isolated ions in single doped compounds. In codoped samples the same experiments showed that Er3+, Yb3+ pairs are formed. Up-conversion under infrared and red excitation results in emissions between 380 and 670 nm and confirms the results obtained under direct excitation. Finally, other parameters for anti-Stokes emissions have been measured under low power infrared excitation, including the dependence of fluorescence intensity with incident power and temperature.