Lianjie Qin

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.

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.

High-power Nd:GdVO4 laser at 1.34 μm end-pumped by laser-diode-array

Abstract A diode-end-pumped high-power Nd:GdVO 4 laser operating at 1.34 μm has been demonstrated. The maximum continuous-wave output power of 4.62 W was obtained at the incident pump power of 14.75 W, with the corresponding optical conversion efficiency of 31.3% and the average slope efficiency of 33.1%. By using the experimentally measured threshold pump power and slope efficiency, the stimulated emission cross-section of Nd:GdVO 4 crystal at 1.34 μm was determined to be 1.78×10 −19 cm 2 .

Growth and properties of mixed crystal Nd:YGdVO4

Abstract Different Gd/Y polycrystalline materials were synthesized by a liquid-phase reaction method and several Nd:YGdVO 4 crystals with low Nd ion concentrations were successfully grown by the Czochralski method. A component analysis was made and the absorption, emission spectra had been measured. The influence of different Gd/Y ratios on the laser properties was also investigated for the first time. The laser experiments have proved that Nd:YGdVO 4 crystals are good laser materials.

LD-pumped actively Q-switched Nd:GdVO4/KTP red laser

Abstract LD-pumped actively Q-switched intracavity frequency-doubled Nd:GdVO4/KTP red laser has been introduced. A maximum red average output power of 0.78 W at 671 nm was obtained at pulse-repetition frequency (PRF) of 15 kHz and the optical conversion efficiency was 6.5%. At the incident pump power of 12 W , the shortest laser pulse occurred at PRF of 15 kHz . Its full-width at half-maximum and the highest peak power were measured to be 35.8 ns and 3.38 kW . The largest single pulse energy of 56.3 μJ was achieved at PRF of 10 kHz . The influence factors on the Q-switched Nd:GdVO4/KTP red laser have been discussed.

Growth, Luminescence Properties and Laser Characterization of Nd:GdVO4 Crystal at 1.34 µm

Using the Czochralski method, Nd:GdVO4 single crystals have been successfully grown with polycrystalline materials synthesized by a liquid-phase method. Luminescence properties of these crystals are determined. The fluorescence lifetime of 0.52 at% Nd-doped GdVO4 crystal is 150 µs. Nd:GdVO4 crystal exhibits a concentration quenching effect. The Nd:GdVO4 crystal samples with different Nd concentrations were used in laser experiments at 1.34 µm pumped by a high-power laser diode (LD). This is the first time report that a laser with a power of up to 4.64 W at 1.34 µm has been achieved with a slope efficiency of 32.9%.

Polarization-resolved study of diode-pumped passively Q-switched Nd:GdVO4 lasers.

By using the natural birefringence of an a-cut Nd:GdVO(4) crystal, we experimentally investigate laser operation under different light polarizations (pi- and sigma-polarized emissions) and compare their performance. The laser performance is further compared with a diode-pumped c-cut Nd:GdVO(4) laser of the same parameters. We show experimentally that the c-cut Nd:GdVO(4) laser could have good passively Q-switched performance in a low-pump-power region but is influenced by other intrinsic laser effects, such as the thermally induced cavity losses; its performance is severely degraded under high pump power. The best passively Q-switched performance obtained in our experiments is from the a-cut pi-polarized laser, which gives the narrowest pulse of 5.4 ns with the highest peak power of 20 kW. Our experimental results show that, to achieve the best performance of the passively Q-switched laser operation, an overall consideration of laser parameters is important.

Growth and properties of Nd:GdVO4 crystal

Abstract A new liquid-phase method synthesizing Nd:GdVO 4 polycrystalline materials was introduced and excellent Nd:GdVO 4 single crystals were successfully grown by the Czochralski method. The effective segregation coefficients of Nd ion in Nd:GdVO 4 crystal were determined. The main defects and the methods of reducing them have been discussed. The fluorescence lifetimes of different Nd ions in crystal were also measured and found the crystal had obvious concentration quenching effect. In the field of high power laser system, a maximum laser output of 14.5 W at 1.06 μm was obtained, and the optical conversion efficiency is 63.0%. Up to 4.93 W laser output at 1.34 μm was also achieved with slope efficiency of 33.3%.

Growth of Nd:GdVO4 Single Crystal and its Laser Output at 1062 nm,1342 nm

A new liquid-phase method synthesizing Nd:GdVO 4 polycrystalline materials was introduced. High optical quality Nd:GdVO 4 single crystals have been successfully grown by the Czochralski method. The effective segregation coefficients of Nd ion in Nd:GdVO 4 crystal have been measured and discussed. Laser outputs at 1.06 μm and at 1.34 μm were achieved when Nd:GdVO 4 crystal samples of 0.52 at% Nd concentration were pumped by a high-power LD. A maximum output of 14.5 W at 1.06 μm has been obtained when the pump power is to 26 W, giving the slope efficiency of 63%. It is reported the first time that up to 4.64 W power laser at 1.34 μm has been achieved with optical conversion efficiency of 31.4% and slope efficiency of 32.9%.

Diode-end-pumped continuous-wave and Q-switched Nd:GdVO4/KTP laser at 671 nm

We have demonstrated a diode-end-pumped continuous-wave and Q-switched Nd:GdVO4 red laser through intracavity frequency-doubling with a type-II phase-matched KTP crystal. The maximum CW output power at 671 nm was measured to be 505 mW at the incident pump power of 12 W, with the corresponding optical conversion efficiency of 4.2%. When the repetition frequency was 15 kHz, the maximum quasi-CW red output power was obtained to be 781 mW, with the corresponding optical conversion efficiency of 6.5%, the shortest pulse width of 65 ns, the highest pulse energy of 52 µJ and the highest peak power of 801 W.