Xianlin Meng

Characterization of the laser crystal Nd:GdVO 4

Nd:GdVO4 crystal was grown by the Czochralski method. The absorption and fluorescence spectra of the crystal were measured at room temperature. The thermal expansion and the specific heat of the crystal were also measured. Laser outputs at 1.06 and 1.34 µm were achieved when a Nd:GdVO4 crystal sample with a high Nd doping concentration was pumped by a low-power laser diode (LD) at 808.5 nm, and visible green and red laser outputs of intracavity frequency doubling at 0.53 and 0.67 µm were also achieved when nonlinear KTiOPO4 and LiB3O5 crystal, respectively, were used. The highly Nd-doped Nd:GdVO4 crystal was pumped by a high-power LD, and a greater than 5-W laser output power at 1.06 µm was obtained. A low-Nd-doping concentration Nd:GdVO4 crystal sample was pumped by a high-power LD, yielding laser output powers at 1.06 and 0.53 µm; 0.53-µm green laser output was obtained when a KTiOPO4 crystal was used, and the output beam’s values were M2=1.76 at an output power of 14.3 W at 1.06 µm and M2=1.55 at an output power of 3.3 W at 0.53 µm. Acousto-optical Q-switched laser outputs at 1.06 and 0.53 µm were also achieved. A thermal lens made from a Nd:GdVO4 crystal was measured; it was weaker than that of a Nd:YVO4 crystal. Some important material parameters, such as temperature-induced changes in refractive index, material constant, thermal-stress resistance figure of merit, and power per unit length at the stress fracture limit, have been estimated.

Improvement of passive Q-switching performance reached with a new Nd-doped mixed vanadate crystal Nd:Gd0.64Y0.36VO4.

Passive Q-switching performance was found to be greatly improved by use of a new Nd-doped mixed vanadate crystal Nd:Gd0.64Y0.36VO4 compared with that achieved with Nd:YVO4 and Nd:GdVO4. At an absorbed pump power of 12 W, an average output power of 2.78 W was obtained at a pulse repetition frequency of 15.4 kHz with an optical conversion efficiency of 23.2%, and the slope efficiency was determined to be 45.5%. The resulting pulse energy, peak power, and pulse width were 181 microJ, 26.6 kW, and 6.8 ns, respectively.

Efficient passive Q-switching operation of a diode-pumped Nd:GdVO 4 laser with a Cr 4+ :YAG saturable absorber

A diode-pumped highly efficient Cr4+:YAG passively Q-switched Nd:GdVO4 laser formed by a plano–concave resonator has been demonstrated. At the highest attainable absorbed pump power of 11.4 W, 4.05 W of average output power, which was two thirds of the maximum corresponding cw output, was achieved with an optical conversion efficiency of 35.5%, and the slope efficiency was determined to be 46.8%, reaching 85% of the magnitude of its cw counterpart. The resulting shortest pulse duration, single-pulse energy, and peak power were found to be 13 ns, 90 μJ, and 7 kW, respectively, with a pulse repetition frequency (PRF) of 45 kHz. Two particularly modified resonator configurations were employed; the largest pulse energy and the highest peak power reached were, respectively, 154 μJ and 11.2 kW at 8.5 W of absorbed pump power. An analytical relation between the PRF and the absorbed pump power is given for a passively Q-switched laser, showing good consistency with experiment with a Nd:GdVO4 laser. The dependence of the operational parameters on the pump power and on the output coupling was also investigated experimentally. Issues involving the criterion for passive Q switching are discussed in some detail for Cr4+:YAG passively Q-switched neodymium-doped vanadate lasers.

Pulse energy enhancement in passive Q-switching operation with a class of Nd:GdxY1−xVO4 crystals

Passive Q-switching operation with a class of Nd:GdxY1−xVO4 crystals has been demonstrated. Compared to Nd:YVO4 and Nd:GdVO4, the pulse energy produced with Nd:Gd0.64Y0.36VO4 under certain conditions was found to be enhanced by factors of 6.0 and 2.5, while the peak power enhanced by factors of 14.7 and 3.6, respectively. At the incident pump power of 9.6 W, 1.3 W of average output power was obtained, with the pulse energy, peak power, and pulse repetition frequency being 166 μJ, 24.5 kW, and 7.7 kHz, respectively.

Thermal and laser properties of Nd:YVO4 crystal

Nd:YVO 4 crystal has been grown by Czochralski method. The data of thermal expansion and specific heat have been measured. The thermal expansion coefficients along a- and c-axis are α 1 = 2.2 × 10 -6 /K, and α 3 = 8.4 × 10 -6 /K respectively. The specific heat is 24.6 cal/mol K at 330 K. The large anisotropy along c- and a-axis of thermal expansion coefficients is explained by the structure of YVO 4 crystal. 921 mW output laser at 1.06 μm has been obtained with a 3 mm × 3 mm × 1 mm crystal sample when pumped by 1840 mW cw laser diode, and the slope efficiency is 55.5%.

Growth, spectra and influence of annealing effect on laser properties of Nd:YVO4 crystal

Abstract Nd:YVO 4 single crystal has been grown by the Czochralski method. The effective segregation coefficients k eff of Nd, Y and V elements have been measured for crystals with different neodymium-doped concentrations. The absorption and fluorescence spectra of Nd:YVO 4 crystal have been measured. The lasers at 1.06 μm have been demonstrated when the crystal samples of annealed and non-annealed Nd:YVO 4 are pumped by laser diode (LD). The influence of annealing effect on laser properties is discussed.

High-power actively Q-switched Nd:GdVO4 laser end-pumped by a fiber-coupled diode-laser array

Abstract An end-pumped acousto-optically Q-switched Nd:GdVO 4 laser has been demonstrated, from which 7.25 W average output power at 1.06 μm at pulse repetition frequency (PRF) of 60 kHz was obtained with an optical conversion efficiency of 38.1% and an averaged slope efficiency of 43.5%. At incident pump power of 17 W, the highest single pulse energy and peak power were achieved when the laser was operated at a PRF of 10 kHz, and were determined to be 340 μJ and 26.2 kW, respectively. The shortest laser pulse with FWHM width of 11 ns was observed at PRF of 20 kHz. Through intracavity frequency doubling, we obtained 2.18 W average green output power with pulse width of 45 ns at a PRF of 25 kHz, the corresponding optical conversion efficiency was 21.8%, and the resulting single pulse energy and peak power were determined to be 87.2 μJ and 1.94 kW, respectively. The results of theoretical calculations on the basis of rate equations are also presented, showing close consistency with the experimental data.

Diode-pumped cw tunable Er3+:Yb3+:YCOB laser at 1.5–1.6 μm

Abstract Laser emission at 1.55 μm has been achieved for the novel laser-nonlinear optical crystal Er:Yb:YCa 4 O(BO 3 ) 3 operated at room temperature, and pumped by a 976 nm diode. A tunable range of 23 nm (1535–1558 nm) was realized with a 50 μm etalon.

Investigations on the Growth and Laser Properties of Nd:GdVO4 Single Crystal

In this paper, we report the growth of laser crystal Nd:GdVO 4 by the Czochralski method, and discuss the morphology of the crystal. The polarization absorption and emission spectra of Nd:GdVO 4 were measured. The lifetime of the Nd:GdVO 4 at 1064 nm is 100 μs. An output power up to 1 W at 1064 mn has been achieved with a 3 mm × 3 mm × 1 mm crystal sample when pumped by a 1.9 W cw laser diode.

Deterministic chaos in a diode-pumped Nd:YAG laser passively Q switched by a Cr 4+ :YAG crystal

We report the experimental observation and numerical simulation of deterministic chaos in a diode-pumped Nd:YAG solid-state laser that is passively Q switched by a Cr4+:YAG crystal saturable absorber. We show that apart from the stable Q-switched operation the laser can also exhibit complicated nonlinear dynamics, including the period-doubling route to chaos and periodic windows.