Guohua Jia

Spectroscopic properties of Er3+ transitions in SrWO4 crystal

Er3+:SrWO4 crystal of good optical quality was grown by Czochralski technique method. Polarized absorption and emission spectra of Er3+ ions in SrWO4 crystal have been investigated. The Judd-Ofelt (JO) theory was applied to the polarized absorption spectra of Er3+:SrWO4 to obtain the three JO parameters: Ω2=7.41×10−20cm2, Ω4=0.25×10−20cm2, and Ω6=1.71×10−20cm2. The radiative probabilities, radiative lifetimes, and branch ratios of Er3+:SrWO4 were calculated. The stimulated emission cross sections of the potential laser transitions at 1535nm were determined using the reciprocity method and the Fuchtbauer-Ladenberg formula, and the potential laser gain versus wavelength for the I13∕24→I15∕24 transition has been estimated and discussed.

Spectroscopic properties of Pr3+ ions in NaGd(WO4)2 crystal

A Pr3+-doped NaGd(WO4)2 single crystal has been grown by the Czochralski technique along the (0 0 1) orientation. The refractive indices were measured precisely as a function of wavelength. A Raman spectrum, polarized absorption spectra, fluorescence spectra, and fluorescence decay curve have been recorded at room temperature. The standard and modified Judd-Ofelt theories have been performed to analyze the absorption spectra to determine the spectroscopic parameters, including the Judd-Ofelt intensity parameters Ωt (t=2,4,6), radiative transition probabilities, radiative lifetimes, and branching ratios. The stimulated emission cross sections and fluorescence lifetime of the promising laser level were obtained.

Optical spectroscopy of Ca3Gd2(BO3)4:Nd 3+ laser crystal

Ca3Gd2(BO3)4:Nd3+ crystals of high optical quality with a size up to 20u2009×u200950u2009mm were grown by the Czochralski method. The absorption spectra of the crystal in three mutually perpendicular arbitrary directions were measured. Based on Judd–Ofelt and TPM methods, the intensity parameters Ω t (tu2009=u20092,u20094,u20096), the experimental and theoretical oscillator strengths, the radiative transition rates, radiative lifetime and fluorescent branching ratios of Nd3+ from 4F3/2 to 4IJ, were obtained. The fluorescence spectrum and decay curve under excitation at 808u2009nm were also measured. The stimulated emission cross-section and radiative quantum efficiency were also calculated.

Optical properties of Er3+ doped Ca3(BO3)2 crystal

The polarized absorption, emission spectra, and the fluorescence decay curve of Er3+ ions in the anisotropic Ca3(BO3)2 crystal were investigated at room temperature. The experimental oscillator strengths for the transitions from the ground state to excited states were compared with the theoretical electric dipole oscillator strengths calculated from the Judd-Ofelt [Phys. Rev. 127, 750 (1962); J. Chem. Phys. 37, 511 (1962)] theory. The emission cross sections and gain cross sections of the π and σ spectra were determined for the H13∕24→H15∕24 transition of special interest for laser application.

Optical and thermal properties of Co2+:ZnWO4 crystal

The crystal of ZnWO4 doped with Co2+ has been grown by the Czochralski technique. The orientation procedure was presented. Along the crystallographic axes, the principal coefficients of thermal expansion and absorption spectra were measured and discussed. Based on the data, the crystal field parameter 10Dq, Racah parameter B, as well as the absorption cross sections were calculated. The nonlinear dependence of optical absorption on concentration of cobalt ions was found and discussed in single crystal Co2+:ZnWO4. The results indicate that inner defects such as natural cleavage or slip faces in crystal are important in the study of optical and thermal properties.

Spectroscopic assessment of Tm3+:GdAl3(BO3)4 crystal as a potential diode pumped laser near 1.9μm

The spectroscopic properties of GdAl3(BO3)4:Tm3+ single crystal for the Tm3+ transition near 1.9μm are presented. The absorption cross section, the emission cross section, and the potential laser gain near 1.9μm are investigated for both σ and π polarizations. The broad absorption band at about 797nm and high value of the above cross section are promising features for obtaining a laser diode pumped Tm3+ laser. The maximum emission cross sections are 1.29×10−20 and 6.60×10−20cm2 at 1.85μm for the σ and π polarizations, respectively. The potential laser gain curves indicate that more than 200nm tunability range is expected for this material.