Sensitization ofEr3+emission at1.5μmbyYb3+inKYb(WO4)2single crystals

Abstract

We present our recent achievements in the growth and spectroscopic characterization of $\mathrm{KYb}({\mathrm{WO}}_{4}{)}_{2}$ crystals doped with erbium ions (hereafter KYbW:Er). We grew single crystals of KYbW:Er at several erbium concentrations with optimal crystalline quality by the top-seeded-solution growth (TSSG) slow-cooling method. We carried out spectroscopic measurements related to the polarized optical absorption and optical emission at room temperature (RT) and low temperature (6 K). The splitting of the excited energy levels and the ground energy level of erbium in KYbW were determined, derived from the absorption and emission measurements at 6 K, respectively. We determined the near infrared, around $1.5\ensuremath{\mu}\mathrm{m}$ $(6667{\mathrm{cm}}^{\ensuremath{-}1}),$ emission channels from the emission spectrum, and used the reciprocity method to calculate a maximum emission cross section of $2.7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}20}{\mathrm{cm}}^{2}$ for the polarization parallel to the ${N}_{m}$ principal optical direction for the $1.534\ensuremath{\mu}\mathrm{m}$ $(6519{\mathrm{cm}}^{\ensuremath{-}1})$ infrared emission. We measured the lifetime of the ${}^{2}{\stackrel{\ensuremath{\rightarrow}}{{F}_{5/2}}}^{2}{F}_{7/2}$ transition of ytterbium and the ${}^{4}{\stackrel{\ensuremath{\rightarrow}}{{I}_{13/2}}}^{4}{I}_{15/2}$ transition of erbium at RT for several erbium concentrations. Finally, we present the Judd-Ofelt calculations for the KYbW:Er system.