RED LASER-INDUCED UP-CONVERSION MECHANISMS IN HO3+ DOPED LAF3 CRYSTAL

In this work, the up-conversion properties of the Ho3+-doped LaF3 upon excitation by a cw red dye laser are reported. Ten groups of emission lines have been detected over a wide spectral range from 13 000 to 22 000 cm(-1). Five of them are up-conversion emissions arising from fou r energy levels: (5)G(4), (5)G(6), F-5(3) and S-5(2)(F-5(4)). The stro ngest up-conversion was observed for the green emission corresponding to the S-5(2)(F-5(4)) --> I-5(8) transition. The up-conversion mechani sm is a sequential two-photon absorption via the I-5(7) level upon exc ited state absorption (ESA) excitation. However, when excited into gro und state absorption (GSA) transitions; two energy transfers involving either two Ho3+ ions excited in the F-5(5) multiplet or one in F-5(5) and the other in I-5(6) multiplets were suggested. (C) 1998 Elsevier Science B.V. All rights reserved.