Synthesis and optical properties of Tb3+ doped CdF2 single crystals

Abstract

• Terbium doped CdF 2 single crystals grown by Bridgman technique. • Absorption, excitation and emission spectra recorded at room temperature. • Spectroscopic properties investigated by use of the Judd–Ofelt theory. • Transition probability, radiative lifetimes, quantum efficiency and branching ratios are calculated. • Emission cross-section is measured by use of Füchtbauer–Ladenburg theory. This paper reports the optical analysis of Tb 3+ doped CdF 2 single crystals. The pulled crystals were prepared by use of the Bridgman technique from a vacuum furnace in fluoride atmosphere. Absorption, photoluminescence excitation and emission spectra were recorded at room temperature. The Judd–Ofelt (JO) intensity parameters Ω 2 , Ω 4 and Ω 6 for 4f–4f transitions of Tb 3+ ions were computed from the optical absorption spectra using UV, visible and near infrared transitions. These parameters were then used to calculate the radiative transition probabilities ( A JJ ′ ), branching ratios ( β JJ ′ ) and radiative lifetimes of the two main laser emitting levels 5 D 3 and 5 D 4 of Tb 3+ ions. The obtained spectroscopic properties are compared to those of Tb 3+ transitions in other hosts. The excitation spectrum in the UV–Visible spectral range is very close to the absorption spectrum indicating that all observed absorption levels can excite the green emission of Tb 3+ corresponding to 5 D 4 → 7 F 5 transition. The emission spectra exhibit a weak blue emission and a strong green emission in the spectral range 370–460 nm and 478–612 nm which are assigned to 5 D 3 → 7 F J ( J = 6, 5, 4, 3, 2) and 5 D 4 → 7 F J ( J = 6, 5, 4, 3) transitions of Tb 3+ , respectively. The green emission 5 D 4 → 7 F 5 at 532 nm having an emission cross-section equal to 8 × 10 −22 cm 2 which is three times more than the transition 5 D 3 → 7 F 5 .