Effect of temperature on optical spectra and relaxation dynamics of Sm3+ in Gd3Ga5O12 single crystals

• Influence of temperature on optical properties of the Gd3Ga5O12:Sm single crystals.
• Analysis of absorption and emission spectra as well as luminescence lifetimes.
• Estimation of energies of crystal field components of Sm3+ in the Gd3Ga5O12 crystal.
• Study on energy transfer phenomena using the classical Inokuti–Hirayama model.

Single crystals of Gd3Ga5O12 (GGG) doped with 2 at.% and 10 at.% of Sm3+ were fabricated by the Czochralski method. Optical absorption and emission spectra as well as luminescence decay curves for these crystals were recorded at different temperatures ranging from 5 K to 300 K. The energies of the crystal field sublevels of selected multiplets were determined based on optical spectra recorded at T = 5 K. It has been found that widths of spectral lines related to transitions between individual crystal field levels of multiplets involved increase by factors of 5–7 when the sample temperature grows from 5 K to 300 K. In contrast to this the positions of spectral lines appear to be independent of temperature. Temperature dependence of the 4G5/2 luminescence lifetime was determined for both concentrations of samarium. Luminescence decay curves follow a single-exponential time dependence when Sm3+ concentration amounts to 2 at.% but a non-exponential decay kinetic and efficient quenching process were observed in highly-doped sample. The Inokuti–Hirayama classical energy transfer model was utilized successfully to account for time dependence of an experimental decay curves recorded for GGG:10 at.% Sm crystal.