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End-pumped by a single-stripe 805-nm diode laser, a maximum continuous-wave output power of 290 mW with slope efficiency of 42% and 90 mW with slope efficiency of 44% around 2 µm were achieved in a 1.6-mm-thickness, unprocessed 7.2 at.% Tm3+:BaGd2(MoO4)4 cleavage plate in a hemispherical and plano–plano cavities, respectively, when the absorbed pump power was 830 mW. The dependence of the polarization of output laser on the output coupler transmission was investigated. The influence of upconversion on the laser performance was analyzed. The results show that the unprocessed Tm3+:BaGd2(MoO4)4 cleavage plate is a promising 2-µm laser gain medium pumped by diode laser around 808 nm. [ABSTRACT FROM AUTHOR]

A Pr3+:NaGd(MoO4)2 single crystal has been grown by the Czochralski method. The polarized absorption spectra, polarized fluorescence spectra, and fluorescence decay curves of the crystal were measured at room temperature. The Judd–Ofelt intensity parameters Ω t, q ( t=2,4,6) and the spectroscopic parameters related to the 3 P 0 and 1 D 2 multiplets were obtained and analyzed. The decay mechanisms for the 3 P 0 and 1 D 2 multiplets were also discussed. [ABSTRACT FROM AUTHOR]

An Er3+:Bi2(MoO4)3 single crystal has been grown by the Czochralski technique. The Stark sublevels of the 4I15/2 and 4I13/2 multiplets of Er3+ ions in the crystal were determined. The polarized absorption spectra, polarized fluorescence spectra, and fluorescence decay curve of the crystal were measured at room temperature and the relevant spectroscopic parameters, including the Judd–Ofelt intensity parameters, spontaneous emission probability, fluorescence branching ratio, radiative lifetime, and stimulated emission cross section, were estimated. The effect of re-absorption on the spectroscopic parameters was discussed. When the crystal was excited at 977 nm, up-conversion green fluorescence was observed and discussed. [ABSTRACT FROM AUTHOR]

An Er3+/Yb3+-codoped Li6Y(BO3)3 crystal was grown by the Czochralski method. The polarized absorption spectra and the fluorescence decay curve were recorded. The efficiency of energy transfer from Yb3+ to Er3+ ions was estimated. Quasi-continuous-wave output power of 325 mW at 1594 nm was realized under the absorbed pump power of 10.4 W in a hemispherical cavity. The absorbed pump threshold and slope efficiency of the laser are 6.0 W and 7.2%, respectively. [ABSTRACT FROM AUTHOR]

A 1.2 mm thick microchip cleaved from a 1.2 at.% Nd3+: BaGd2(MoO4)4 crystal was used as the laser gain medium directly. The laser cavity mirrors were coated on the microchip without cutting and polishing. In the 1.06 μm quasi-CW laser operation, the microchip was pumped by a Ti:sapphire laser with a duty cycle of 10%, the threshold is 10 mW, and the slope efficiency is 50%. In the CW laser operation pumped by a diode laser, the threshold and slope efficiency are 140 mW and 33%, respectively. The results demonstrate that the unprocessed surfaces of the cleaved microchip have good enough flatness and parallelism for laser operation. [ABSTRACT FROM AUTHOR]

A Bi2(MoO4)3 single crystal doped with Pr3+ ions has been grown by the Czochralski technique. The polarized absorption and fluorescence spectra as well as the fluorescence decay curve of Pr3+ ions in the crystal were measured at room temperature. The spectroscopic parameters, including the Judd–Ofelt intensity parameters Ωt (t=2, 4, and 6), spontaneous emission probabilities, fluorescence branching ratios, radiative lifetimes, stimulated emission cross sections, and fluorescence quantum efficiencies, were calculated. The spectral properties related to laser performance of this crystal were analyzed. The 1 D 2 multiplet of the crystal may be a good upper level for a solid-state laser. [ABSTRACT FROM AUTHOR]

A Pr3+-doped La2(WO4)3 crystal grown by the Czochralski method has been investigated as a promising laser material. The principal axes of the optical indicatrix and Pr3+ concentration of the crystal were determined. The polarized absorption, fluorescence spectra and fluorescence decay curves of the main emission multiplets of the crystal were measured at room temperature. The spectroscopic parameters were obtained by the modified Judd–Ofelt theory combined with the normalized method. The peak stimulated emission cross-sections of the major emission lines were estimated. The good spectroscopic properties imply that the Pr3+:La2(WO4)3 crystal is a potential laser gain medium for solid-state laser and self-stimulated Raman laser applications. [ABSTRACT FROM AUTHOR]

Passively Q-switched laser oscillation at 1060 nm from an unprocessed Nd:LaB3O6 cleavage microchip with a Cr4+:YAG saturable absorber has been demonstrated. The influence of absorbed pump power, output coupler transmission and cavity length on the output pulse characteristics has been investigated. For a plano-concave cavity with a cavity length of 28 mm, pulse with 100 mW average output power, 4.0 μJ energy, 17 ns duration, 25 kHz repetition rate, and 0.24 kW, peak power was obtained at the absorbed pump power of 1.42 W and output coupler transmission of 3.5%. For a plano-plano cavity with a cavity length of 5 mm, pulse with 85 mW average output power, 2.1 μJ energy, 2.3 ns duration, 40 kHz repetition rate, and 0.89 kW, peak power was obtained at the absorbed pump power of 1.42 W and output coupler transmission of 5.6%. Because a chopper with a 5% duty cycle was employed in the experiments to reduce the influence of pump-induced thermal loading, the above average output powers were obtained at the 5% duty cycle and extrapolated to 100%. [ABSTRACT FROM AUTHOR]

An Er:Yb:Sr3Gd2(BO3)4 crystal was grown by the Czochralski method. The polarized spectral properties of the crystal were investigated, including the polarized absorption and fluorescence spectra and fluorescence decay. The fluorescence quantum efficiency of the upper laser level 4I13/2 of Er3+ ions and the efficiency of the energy transfer from Yb3+ to Er3+ ions were calculated. End-pumped by a diode laser at 970 nm in a hemispherical cavity, a 1.6 W quasi-cw laser at 1.5–1.6 μm with a slope efficiency of 18% and an absorbed pump threshold of 5.9 W was achieved in a 1.8-mm-thick Z-cut Er:Yb:Sr3Gd2(BO3)4 crystal. This crystal has a flat and broad gain curve at 1.5–1.6 μm and so is also a potential gain medium for tunable and short pulse lasers. [ABSTRACT FROM AUTHOR]

Polarized spectral properties of Er3+:NaGd(WO4)2 single crystal are reported. The crystal was grown by the Czochralski method. The Judd–Ofelt theory was applied to analyze the polarized absorption spectra and then calculate the spontaneous emission probabilities, radiative lifetimes, and branching ratios. Fluorescence decay curves of the 4 I 13/2, 4 I 11/2, and 4 S 3/2 multiplets for the Er3+ ions were measured. Stimulated emission cross-sections of the 4 I 13/2→4 I 15/2 transition obtained by the Fuchtbauer–Ladenberg formula and the reciprocity method were compared. Multi-phonon relaxation rates of the crystal were estimated. Green up-conversion fluorescence around 531 and 552 nm was observed, and the possible up-conversion mechanisms were proposed. [ABSTRACT FROM AUTHOR]