Diode end-pumped Q-switched high-power intracavity frequency-doubled Nd:GdVO4/KTP green laser

A diode-laser-array end-pumped acousto-optically Q-switched intracavity frequency-doubled Nd:GdVO₄/KTP green laser, formed with a three-mirror folded resonator, has been demonstrated. With 15 W of pump power incident upon the Nd:GdVO₄ crystal, a maximum average green output power of 3.75 W was obtained at 50 kHz of pulse repetition frequency, giving an optical conversion efficiency of 25%, whereas the effective intracavity frequency-doubling efficiency was determined to be 72%. At the incident pump power of 12.8 W, the shortest laser pulse was achieved at a pulse repetition rate of 10 kHz, the resulting pulse width, single pulse energy, and peak power were measured to be 35 ns, 108 μJ, and 3.1 kW, respectively. Received: 18 May 2000 / Published online: 20 September 2000     

All solid-state passively Q-switched frequency-doubled intra-cavity Nd: GdVO4/KTP laser

In this paper, laser frequency-double and passive Q-switching are studied. The optimum coupling at endpump and optimum design of resonator are also investigated. The maximum output power of TEM00 is 1.68 W at 1.06-μm wavelength. Optic-optic conversion efficiency is 48.6%, and the slope efficiency is 56.3%. The maximum output of green light is 0.235 W. The smallest pulse-width of green light is 27.42 ns, optic-optic conversion efficiency of green light is 7%, and beam quality factor M2 ＜ 1.2. Thermal lens effect is discussed.     

Pulse compression in AO Q-switched diode-pumped Nd:GdVO4 laser with Cr4+:YAG saturable absorber

By simultaneously using both an acoustic-optic (AO) modulator and a Cr⁴⁺:YAG saturable absorber in the cavity, for the first time, a diode-pumped doubly Q-switched Nd:GdVO₄ laser has been realized. The pulse duration is obviously compressed in contrast to the actively acoustic-optic Q-switched laser. By considering the Gaussian transversal distribution of the intracavity photon density and the longitudinal distribution of the photon density along the cavity axis as well as the influence of turnoff time of the acoustic-optic (AO) Q-switch, we provide the coupled rate equations for a diode-pumped doubly Q-switched Nd:GdVO₄ laser with both an acoustic-optic (AO) modulator and a Cr⁴⁺:YAG saturable absorber. These coupled rate equations are solved numerically, and the dependence of pulse width, pulse energy and peak power on the incident pump power at different pulse repetition rates is obtained. The numerical solutions of equations agree well with the experimental results.This revised version was published online in August 2005 with a corrected cover date.     

Pulse compression in AO Q-switched diode-pumped Nd:GdVO4 laser with V3+:YAG saturable absorber

By simultaneously using both an acoustic-optic (AO) modulator and a V³⁺:YAG saturable absorber in the cavity, for the first time to our knowledge, a diode-pumped doubly Q-switched Nd:GdVO ₄ laser has been realized. The dependence of pulse width, pulse energy and peak power on the incident pump power at determinate pulse repetition rate are measured. Under the absorbed pump power of 8.59 W, the pulse temporal profile of the AO-switching with the pulse duration of 14.5 ns, the double Q-switching with pulse duration of 7.6 ns at 10 kHz, and the passive Q-switching with pulse duration of 22.3 ns are obtained. The pulse duration is obviously compressed in contrast to the purely actively AO Q-switched laser or the purely passively Q-switched laser with V³⁺:YAG.     

532 nm diode-pumped doubly Q-switched Nd:YVO4/KTP laser with electro-optic modulator and GaAs saturable absorber

A diode-pumped doubly Q-switched Nd:YVO₄ laser operating at 532 nm with an electro-optic (EO) modulator and a GaAs saturable absorber is presented. This laser can generate more symmetric and shorter pulses compared with those modulated by a single EO Q-switcher. A symmetry factor is defined to describe the temporal symmetry of the pulse profile. At the pump power of 10 W, a 4.2-ns pulse with a symmetry factor of 1.053 and a peak power of 33.7 kW is obtained. A rate equation model has been developed in order to explain the experimental results, in which the influences of population-inversion density on laser character are taken into account, and it leads to a good agreement with the experimental data.     

A compact diode-pumped Q-switched and mode-locked Nd:GdVO4 laser based on SESAM

We report a compact passively Q-switched and Mode-locked Nd:GdVO₄ laser based on a semiconductor saturable absorber mirrors (SESAM). At a pump power of 12 W, the average output power was obtained to be 1.8 W with the repetition rate of the Q-witched envelope 80 kHz and 500 ns pulse width. The mode-locked pulses interval within the Q-switched envelope was about 1ns, corresponding to the high repetition of 1 GHz.     

Compact and efficient diode-pumped passively Q-switched Nd:GdVO_4 laser at 1.06μm

Diode-pumped passively Q-switched Nd:GdVO4/Cr4+:YAG lasers with a simple flat-flat cavity were demonstrated. The maximum average output power at 1.06 μm was 1.25 W. The highest peak power and pulse energy were 7.56 kW and 75μJ, respectively, with the pulse repetition rate of 11.1 kHz and pulse width of 10 ns at the incident pump power of 8 W.     

912 nm laser operation in diode-pumped grown-together composite Nd:GdVO4/GdVO4 crystal

Novel grown-together Nd:GdVO₄/GdVO₄ composite crystals were presented for the first time, which would be longitudinally pumped by 808 nm diode-laser to efficiently operate on continuous-wave (CW) 912 nm laser at room temperature. The maximum output power of 8.15 W at 912 nm laser was obtained successfully at the absorbed pump power of 28.0 W, giving the corresponding optical-to-optical conversion efficiency of 29.1% and the average slope-efficiency of 44.2%. Comparative experimental results show that the laser performance was influenced significantly by the Nd³⁺-doped concentration of the crystals, which would be optimized according to its energy-transfer upconversion (ETU) spectrum.     

Laser-diode-pumped doubly Q-switched Nd:GdVO4/KTA intracavity optical parametric oscillator

By using an acousto-optic (AO) modulator and a Cr⁴⁺:YAG saturable absorber, a high repetition rate doubly Q-switched noncritically phase-matched KTiOAsO₄ (KTA) intracavity optical parametric oscillator (IOPO) at 1.50 μm is realized. In comparison to AO Q-switched IOPO, the lower threshold energy, the higher output average power, the narrower pulse width and the higher peak power from the doubly Q-switched IOPO can be obtained.     

Diode-pumped, Cr:YAG passively Q-switched and mode-locked Nd:YVO_4/KTP green laser

The phenomena of simultaneous Q-switching and mode-locking in a diode-pumped Nd:YVO4/Cr:YAG/ KTP green laser are reported and discussed in this paper. With 5.3-W pump power, by using a nearly hemispherical cavity (the cavity length is only 97 mm), the results of modulation depth of 70% and the period of 0.6 ns are obtained, the output power and the repetitive frequency of Q-switched pulse are 90 mW and 12 kHz, respectively.     

Diode-pumped doubly passively Q-switched Nd:LuVO4/KTP green laser with Cr:YAG and GaAs saturable absorbers

A diode-pumped doubly passively Q-switched intracavity-frequency-doubling Nd:LuVO₄/KTP green laser with Cr⁴⁺:YAG and GaAs saturable absorbers is demonstrated. This laser can generate the shorter pulse width with higher peak power compared with the singly passively Q-switched green laser with Cr⁴⁺:YAG or GaAs saturable absorber. The relations between the pulse symmetry and the ratio of the small-signal transmissions of two saturable absorbers are investigated. By reasonably choosing the small-signal transmissions of both saturable absorbers, the doubly passively Q-switched green laser can generate the much more symmetric pulse profile. The coupled rate equations are used to simulate the passively Q-switched process of the green laser by considering the Gaussian transversal and longitudinal distributions of the intracavity photon density. The numerical results of the equations are consistent with the experimental results.     

Wood engraving by Q-switched diode-pumped frequency-doubled Nd:YAG green laser

Laser deep engraving is one of the most promising technologies to be used in wood carver operations. In this method, a laser beam is used to ablate a solid wood bulk, following predetermined patterns. The sculpture is obtained by repeating this process on each successive thin layer. Obviously, in order to achieve larger material removal rates, the process needs a controllable variation of the depth to carve a 3D (three dimensional) profiles.The degree of precision of the shape, the removal rate and the surface quality during the engraving process strictly depend on the materials properties, the laser source characteristics and the process parameters.The aim of this work is to investigate the influence of the process parameters on the material removal rates by engraving panels made of different types of wood using a Q-switched diode-pumped Nd:YAG green laser working with a wavelength λ=532 nm. The examined parameters were: the mean power that depends on the pulse frequency, the beam speed and the number of laser scansions, also called repetitions. The working parameters and the engraved depth were related and an energy-based model was proposed in order to predict the latter.Experimental results showed that the Q-switched diode-pumped frequency-doubled Nd:YAG green laser can be successfully used to machine different types of wood, obtaining decorative drawing and 3D engraved geometries without burning. However, an accurate selection of the wood types and the process parameters is necessary in order to obtain deep engraving without carbonization and a homogeneous carving.     

Optimization of diode-pumped passively Q-switched mode-locked c-cut Nd:GdVO4 laser with a GaAs saturable absorber

By considering the single-photon absorption (SPA) and two-photon absorption (TPA) processes in the GaAs saturable absorber, the coupled rate equations for a diode-pumped passively Q-switched and mode-locked (QML) laser with GaAs coupler under Gaussian approximation are given. The key parameters of an optimally coupled passively QML laser can be obtained by numerically solving these equations. These key parameters include the parameters of the gain medium, the saturable absorber and the resonator, which can maximize the pulse energy of singly Q-switched envelope. Sample calculations for a diode-pumped passively Q-switched mode-locked c-cut Nd:GdVO₄ laser with a GaAs saturable absorber are presented to demonstrate the optimal method applicable.     

Theoretical and experimental study of a diode-pumped doubly Q-switched intracavity-frequency-doubling Nd:LuVO4/KTP green laser with acoustic-optic (AO) modulator and GaAs saturable absorber

By considering the Gaussian transversal and longitudinal distributions of the intracavity photon density as well as the walk-off effect of KTP crystal, the coupled rate equations of the doubly Q-switched intracavity-frequency-doubling Nd:LuVO₄/KTP green laser with acoustic-optic (AO) modulator and GaAs saturable absorber are given. These equations are solved numerically and the doubly Q-switched green laser characteristics, such as the pulse width and the pulse symmetry, have been obtained. In the experiment, a diode-pumped doubly Q-switched intracavity-frequency-doubling Nd:LuVO₄/KTP green laser with AO and GaAs is presented. This doubly Q-switched green laser can generate the almost absolutely symmetric pulse profile with the shorter pulse width and the higher power than the singly Q-switched green laser. The experimental results are in agreement with the theoretically numerical calculations.     

Diode-pumped passively Q-switched intracavity frequency doubled Nd:GdVO4/KTP green laser

A compact diode-pumped passively Q-switched intracavity frequency-doubled Nd:GdVO₄/KTP green-pulse laser was demonstrated, using Cr⁴⁺:YAG as a saturable absorber in a simple flat–flat cavity. With a 5.9 W incident pump power, a passively Q-switched green laser was obtained with an average power of 397 mW, repetition rate of 40 kHz, and pulse width of 40 ns, when the initial transmission of Cr⁴⁺:YAG was 85%. The shortest pulse width of 30 ns, the highest green peak power of 696 W and the maximum pulse energy of 21 μJ were obtained when the initial transmission of Cr⁴⁺:YAG was 70%. Under CW green operation, we obtained 440 mW output power.     

激光二极管抽运Nd∶YVO4和KTP倍频产生单频绿光激发器

报道了一种激光二极管抽运、KTP倍频的Nd∶YVO4激光器,采用折叠腔,实现了稳定的高输出单频倍频运转,绿光输出功率达到102 mW,转换效率为10.7 %.     

Control of the pulse width in a diode-pumped passively Q-switched Nd:YVO<Subscript>4</Subscript>/KTP green laser with GaAs saturable absorber

By varying the positions of the saturable absorber in the laser axis and the pump beam waist in the gain medium, respectively, we have theoretically and experimentally studied the control of the pulse width in a diode-pumped passively Q-switched Nd:YVO₄/KTP green laser with GaAs saturable absorber. A rate equation model is introduced, in which the intracavity photon density is assumed to be Gaussian spatial distribution, the longitudinal variation of the intracavity photon density and the pump beam spatial distribution are also considered. The experimental results are consistent with the numerical calculations of the rate equations.     

Efficient diode-pumped actively Q-switched Nd:YAG/BaWO4 intracavity Raman laser

Barium tungstate (BaWO4) is employed to achieve efficient stimulated Raman scattering conversion in a compact diode-pumped actively Q-switched Nd:YAG laser. With an incident pump power of 9.2 W, 1.56 W of 1181 nm first-Stokes average output power was generated at a pulse repetition rate of 20 kHz, corresponding to an optical-to-optical conversion efficiency of 16.9%.     

LD泵浦的Nd:GdVO4/KTP腔内倍频激光器

基于对Nd:GdVO4晶体热焦距的测量及其1.06 μm激光基本性能,用三镜折叠腔研究了半导体激光器(LD)泵浦的Nd:GdVO4/KTP晶体的内腔倍频性质.当用从直径为200 μm的单光纤输出的低功率的半导体激光泵浦时,绿光的阈值是26 mW,光光转换效率为17.3%.当用从直径为1.55 mm的光纤束输出的高功率的半导体激光泵浦时,绿光的阈值是200 mW,光光转换效率为19.35%.