Liu Wenpeng

Luminescence and Thermal Properties of Er:GSGG and Yb,Er:GSGG Laser Crystals

Er3+-doped and Yb3+/Er3+ co-doped Gd3Sc2Ga3O12 (abbreviated as Er:GSGG and Yb,Er:GSGG, respectively) laser crystals are investigated by using a combination of spectroscopic measurements and thermal characterizations. An absorption peak of Yb, Er: GSGG crystal shifts to 970 nm and its absorption band broadens obviously, which makes the crystal suitable for pumping by a 970 nm laser diode (LD). This crystal also exhibits a shorter lifetime of a lower laser level, a larger emission cross section and higher thermal conductivity than those of Er: GSGG. All these factors suggest that Yb3+/Er3+ co-doping has a positive effect on improving the spectroscopic and thermal performances in GSGG based laser crystals, and imply that double-doped Yb, Er: GSGG crystal is a potential candidate as an excellent LD pumped 2.79 mu m laser material.

Calculating Hamiltonian parameters for Yb3+ in a low-symmetry lattice site, and fitting the structure and levels of Yb3+:RETaO4 (RE = Gd, Y, and Sc)

An iterative method is used to find the values of the Hamiltonian parameters for Yb3+ in a given low-symmetry crystalline site. Samples of Yb3+:RETaO4 (RE = Gd, Y, and Sc) were prepared and their structures were determined. Based on the obtained structural data, their orbital-spin parameters and crystal field parameters were fitted by the superposition model (SM). Using the crystal field parameters obtained by the SM fitting as the initial parameters, the Hamiltonian parameters were fitted iteratively. The calculated and experimental energy levels for Yb3+:RETaO4 are consistent, and the maximal mean-root-square deviation is only 2.84 cm−1, indicating that the method is effective to determine the Hamiltonian parameters of Yb3+ in low-symmetry crystalline sites.

Method for fitting crystal field parameters and the energy level fitting for Yb3+ in crystal SC2O3

A method to compute the numerical derivative of eigenvalues of parameterized crystal field Hamiltonian matrix is given, based on the numerical derivatives the general iteration methods such as Levenberg–Marquardt, Newton method, and so on, can be used to solve crystal field parameters by fitting to experimental energy levels. With the numerical eigenvalue derivative, a detailed iteration algorithm to compute crystal field parameters by fitting experimental energy levels has also been described. This method is used to compute the crystal parameters of Yb3+ in Sc2O3 crystal, which is prepared by a co-precipitation method and whose structure was refined by Rietveld method. By fitting on the parameters of a simple overlap model of crystal field, the results show that the new method can fit the crystal field energy splitting with fast convergence and good stability.

Study on the growth and luminescence characterization of Cr/Nd:GLSAG crystal

The Cr/Nd:GLSAG crystal were grown by Czochralski method, its structure and luminescence properties were studied, which show that the luminescence properties of Nd³⁺ ions were improved by co-doping Cr³⁺ ions and adjusted by mixed garnet.