Spectroscopic investigation of Nd3+ and Yb3+ in Ca4GdO(BO3)3 crystals

Gadolinium calcium oxoborate Ca4GdO(BO3)(3) (GdCOB) is a new efficient non-linear optical crystal belonging to the rare-earth calcium berate group with general composition Ca4RB3O10 (R = La-Lu, Y). It exhibits efficient second harmonic generation (SHG) properties, a large transparency region and a high damage threshold. The compound Ca4GdO(BO3)(3) crystallises with a monoclinic acentric structure. The space group is Cm. Partial substitution of Gd3+ ions by other lanthanide ions leads to interesting studies of new laser materials. In this paper we consider optical properties of Nd3+ and Yb3+ ions in Ca4GdO(BO3)(3). In this crystal neodymium ions act as donors of excitation energy, whereas ytterbium ions play the role of accepters. We are interested in ion-matrix and ion-ion interactions such as electron-phonon coupling, and Nd-Yb excitation energy transfer. The infrared transmission and Raman scattering spectra were measured and the vibrational assignment is proposed. Absorption, emission and lifetime measurements have been carried out within the 5-300 K temperature range. (C) 2000 Elsevier Science B.V. All rights reserved.