Preparation and systematic spectra analysis of YPO4 crystal co-doped with Er3+ and Yb3+

Abstract

The Er3+:YPO4 crystals co-doped with different concentrations of Yb3+ (7.5 at.% and 11.5 at.%) were successfully grown by high-temperature solution method with Pb2P2O7 as cosolvent. Crystal growth, structures and spectroscopic characterizations, including polarized absorption spectra, polarized fluorescence spectra and lifetime, were systematically explored and compared. The absorption FWHM at around 975 nm is 17.1 nm for σ-polarizations and 12.0 nm for π-polarizations, which makes Er3+/Yb3+:YPO4 crystal suitable for effective pumping by InGaAs laser diode. Based on J-O theory, the spectroscopic parameters, including J-O intensity, oscillator strength, line strength, fluorescence branching ratios, spontaneous transition rates and radiative lifetime were calculated systematically. Furthermore, four intense emission peaks at around 1505, 1537, 1561 and 1586 nm can be observed in the polarized fluorescence spectra. Theoretically, different frequencies interactions between these wavelengths may be used for the application of generating radiation in the range of 2.9–10.2 THz. The results show that Er3+/Yb3+:YPO4 crystal may be a potential laser material of 1.5–1.6 μm.