[Research on raman spectra and energy transfer in Tm3+, Ho3+ single and co-doped YVO4 crystals].
摘要
Raman spectra of Tm3+ :YVO4, Ho3+ :YVO4 and Tm3+: Ho3+: YVO4 crystals were measured at room temperature by HRD-1 double grating monochromator, with the excitation laser beam were parallel and perpendicular to c axis, respectively. For the Ho3+: YVO4, it was found that the Raman spectrum excited by laser beam perpendicular to axis c is stronger than that by parallel excitation, and because 488 nm laser was very close to the absorption peak of Ho3+, the competition between absorption and scattering results in the 475 cm(-1) Raman mode weakening and external mode widening. It was also found that the most probable phonon energy focused on the 880 cm(-1), which was brought about by the breathe mode of (VO4)3-, Like YAG, YVO4 is a kind of crystal with high phonon energy too. Comparing the luminescence of Tm3+ :YVO4 with that of Tm3+: Ho3+: YVO4, it was found that the intensity of Ho3+ 2.09 microm is about 4/5 of that of Tm3+ 1.85 microm, which means the sensitization efficiency of Tm3+ to Ho3+ was as high as up to 80%, and since the overlap between the luminescence of Tm3+ with the absorption of Ho3+ is quite small, the radiative energy transfer between them was very less possible, and most probability, this process was via the nonradiative, phonon-aided cross-relaxation between Tm3+ and near resonance energy transfer between Tm3+ and Ho3+.