Spectroscopy of tetragonal Eu:NaGd(WO4)2 crystal

Abstract

We report on growth and detailed spectroscopic study of Eu3+-doped tetragonal sodium gadolinium double tungstate, Eu:NaGd(WO4)2, a new promising crystal for deep-red lasers. Large-volume crystal doped with 4.9 at.% Eu is grown by Czochralski method along the [001] crystallographic direction. Absorption of Eu3+ ions is studied at room temperature (RT) and at 6 K. For the absorption band related to the 7F1 → 5D1 transition suitable for pumping of Eu:NaGd(WO4)2, the maximum cross-section is σabs = 1.2 × 10−21 cm2 at 535.5 nm with the full width at half maximum (FWHM) of 3.1 nm (at RT, for E || a polarization). For the 5D0 → 7F4 transition, the maximum stimulated-emission cross-section is σSE = 1.6 × 10−21 cm2 at 698.3 nm (RT, E || c polarization). Lifetime of the 5D0 state is 490 ± 10 μs (at RT). Under UV excitation, Eu:NaGd(WO4)2 provides intense red emission with CIE coordinates (x = 0.671, y = 0.329).