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A high-quality Cr:CYA (Cr:CaYAlO 4) single crystal fiber was grown by μ-PD (Micro-Pulling-Down) method. The E//a and E//c polarized excitation spectra of Cr:CYA at room temperature was measured. The crystal field parameters were calculated and the energy level structure of Cr:CYA was analyzed. We also measured the polarization emission spectra and lifetimes at different temperatures and calculated the effective emission cross-section. Based on the above data and Boltzmann law, the thermal distribution between the excited energy levels 2E and 4A 2 at different temperatures was analyzed. The present work may be useful for guiding laser research on Cr:CYA and other Cr3+-doped laser crystals above room temperature. • Cr:CYA single crystal fiber was grown by μ-PD (Micro-Pulling-Down) method. • Excitation spectra and crystal field parameters of Cr:CYA crystals were investigated and analyzed. • The effective emission cross section of Cr:CYA at different temperatures was calculated. [ABSTRACT FROM AUTHOR]

Highlights: [•] Various physical parameters are evaluated and non-linear behavior is observed. [•] Mixed alkali effect is observed in all physical and structural studies. [•] EPR and optical studies confirmed distorted octahedral site symmetry. [•] From optical absorption edges, optical band gap energies and Urbach energies are evaluated. [ABSTRACT FROM AUTHOR]

Highlights: [•] Combined analysis based on crystal field theory and DFT independent methods have been used for (Na, Li)CrSi2O6 crystals. [•] Crystal field parameters modeling and energy levels scheme simulation of two Cr3+-bearing system have been made. [•] Structural and electronic properties of considered materials were predicted. [ABSTRACT FROM AUTHOR]

Highlights: [•] Spectroscopic properties of di-, tri- and tetravalent free 3d ions are analyzed. [•] Relations between the Racah parameters, spin–orbit constant and atomic number are found. [•] Variations of these parameters in several crystals are considered. [ABSTRACT FROM AUTHOR]

Abstract: This paper describes a computational study of extrinsic defect of Sr3Al2O6 induced by trivalent rare-earth dopants. Solution energies for a range of possible doping mechanisms are calculated, and predictions made of doping sites and charge-compensation schemes. It is shown that there are definite trends going along the rare-earth series. Atomistic modeling is used to calculate the symmetry and detailed geometry of the dopant ion-host lattice system, and this information is then used to calculate the crystal field parameters, which are an important indicator in assessing the optical behaviour of the system. The transition levels are then calculated for the Eu3+-substituted material, and comparisons with the experimental results were done. [ABSTRACT FROM AUTHOR]

Highlights: [•] The Eu3+ ion C1 symmetry in the β-diketonate complex is viewed as S 4 symmetry. [•] The Eu3+ site symmetry and electrostatic neutrality are the important features. [•] The signal and magnitude of the parameters are correctly predicted. [•] The Eu3+ ion feels its nearest neighbour merely as negative charges. [ABSTRACT FROM AUTHOR]