Synthesis and optical properties of Tb3+ doped CdF2 single crystals

• Terbium doped CdF2 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 Tb3+ doped CdF2 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 Ω2, Ω4 and Ω6 for 4f–4f transitions of Tb3+ 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 (AJJ′), branching ratios (βJJ′) and radiative lifetimes of the two main laser emitting levels 5D3 and 5D4 of Tb3+ ions. The obtained spectroscopic properties are compared to those of Tb3+ 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 Tb3+ corresponding to 5D4 → 7F5 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 5D3 → 7FJ (J = 6, 5, 4, 3, 2) and 5D4 → 7FJ (J = 6, 5, 4, 3) transitions of Tb3+, respectively. The green emission 5D4 → 7F5 at 532 nm having an emission cross-section equal to 8 × 10−22 cm2 which is three times more than the transition 5D3 → 7F5.