A promising laser crystal Er3+:YPO4 with intense multi-wavelength emission characteristics

The Er3+:YPO4 crystal was grown successfully from Pb2P2O7 solution by the high-temperature solution method. The crystal growth, structures, polarization absorption spectra, polarization fluorescence spectra and lifetime of the grown crystal were discussed in detail. The absorption cross-sections at around 524 nm are 2.93 × 10−20 cm2 for σ-polarizations and 3.19 × 10−20 cm2 for π-polarizations, respectively. Based on Judd-Ofelt theory, the line strength, Judd-Ofelt intensity, spontaneous transition rates, fluorescence branching ratios and radiative lifetime were calculated systematically. Four strong emission peaks with central wavelength at 1505, 1538, 1562 and 1586 nm were observed in the polarized fluorescence spectra. And the emission cross-sections corresponding to these emission peaks range from 0.99 × 10−20 cm2 to 1.66 × 10−20 cm2. The results show that Er3+:YPO4 crystal is a potential laser material applied to 1.5–1.6 μm. Moreover, different frequency interactions between these wavelengths may be used to generate radiation in the range of 2.9–10.2 THz theoretically.