Tm3+/Yb3+ droped YNbO4 power sample was prepared with the molar ratios of 50Nb2O5-(46-x)Y2O3-4Yb2O3-xTm2O3 (x=0.1, 0.2, 0.5, 1, 2) by the high temperature solid state method at 1 300 ℃. Under 980 nm laser excitation, the upconversion luminescence spectra of samples show 478 nm from 1G4→3H6 transition of Tm3+ ions, 645 nm attributed to 1G4→3F4 transition of Tm3+ ions, respectively, and 707 nm emissions assigned to 3F3→3H6 transition of Tm3+ ions. The transition process is estimated by using the relation between the upconversion power and the operating current of the 980 nm laser. The numbers of photons absorbed are 2.72, 2.69 and 2.01. The first two correspond to three-photon absorption processes, and the last one corresponds to two-photon absorption process. The spectral properties of the samples are studied by using Judd-Ofelt theory. Spectral strength parameters Ωt(t=2, 4, 6) were computed based on the absorption peak's area of the absorption spectrum. The theoretical oscillator strength and the experimental oscillator strength were calculated according to the spectrum strength parameters, and the root mean square deviation (δrms) was 1.299×10-7. The transition probability, branching ratio and other parameters of the lower level transition of Tm3+ ion were calculated. The results show that: (1) the 3F4 has a longer level lifetime, which is suitable for up-conversion intermediate level; (2)3H5 has a longer level lifetime, and the transition branching ratio of 3H5→3H6 is close to 100%(96.46%), so this sample can be used to generate 1 216 nm laser. © 2018, Science Press. All right reserved.
