Spectral properties and energy transfer of Yb,Er:GdVO_4 crystal

摘要

GdVO_4 single crystal co-doped with Yb~(3+) and Er~(3+) was grown by the Czochralski method. The X-ray powder diffraction pattern of Yb,Er:GdVO_4 crystal confirms that the as-grown crystal is isostructural with pure GdVO_4 crystal. Its polarized absorption spectra and non-polarized fluorescence spectra were measured at room temperature. The absorption band at 984 nm for π-polarization has an FWHM of about 36 nm, which is favorable for InGaAs LD laser pumping. The spectrum properties of Er~(3+) in Yb,Er:GdVO_4 crystal were investigated based on Judd-Ofelt theory. There is strong energy transfer from Yb~(3+) to Er~(3+) in this crystal. When excited with 980 nm radiation, this crystal emitted strong fluorescence at about 1529 nm and 552.5 nm. The total energy transfer rate and efficiency from Yb~(3+) to Er~(3+) is 3.33 ms~(-1) and 67%, respectively. The energy transfer between Er~(3+) and Yb~(3+) ions is a multistep transfer process, and was investigated based on a random-walk model. The investigation result shows that there is strong cooperative-sensitization effect from Yb~(3+) to Er~(3+), which is the main upconversion energy-transfer process in this crystal.