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A diode-pumped dual-loss-modulated Q-switched and mode-locked (QML) [Nd:GdVO.sub.4]/KTP green laser with an acousto-optic modulator (AOM) and GaAs saturable absorber is presented. The experimental results show that the stability and the peak power of the dual-loss-modulated QML [Nd:GdVO.sub.4]/KTP green laser are significantly improved. The pulse width of the Q-switched pulse envelope in the dual-loss-modulation QML green laser has a compression of 50% compared with that in the singly passively QML green laser with GaAs. By using a hyperbolic secant square function and considering the Gaussian distribution of the intracavity photon density, the coupled equations for diode-pumped dual-loss-modulated QML [Nd:GdVO.sub.4] green laser are given, and the numerical solutions of the equations are in good agreement with the experimental results. [c] 2010 Optical Society of America OCIS codes: 140.3515, 140.3480.

By considering the influence of the turn-off time and the modulation frequency of the acousto-optic (AO) modulator as well as the Gaussian spatial distribution of the photon density, we give a developed rate equation model for a diode-pumped dual-loss-modulated Q-switched and mode-locked (QML) Nd:GdV[O.sub.4] laser with AO modulator and [Cr.sup.4+]:YAG saturable absorber. With this developed model, the dual-loss-modulated QML laser characteristics, such as pulse width and pulse energy, can be numerically simulated, and the theoretical evaluations are in good agreement with the experimental results. [c] 2010 Optical Society of America OCIS codes: 140.3430, 140.3480, 140.3580, 140.3540, 140.4050.

A diode end-pumped doubly Q-switched YV[O.sub.4]/Nd:YV[O.sub.4] laser has been realized for the first time to our knowledge by using both an electro-optic (EO) modulator and a [Cr.sup.4+]:YAG saturable absorber. A 3.8 ns pulse width is generated by this laser under a pump power of 15W at 2kHz, which is obviously compressed in comparison with that of 8.8 ns from a single actively EO Q-switched laser. Under the same conditions, peak power values of 174.7 and 93 kW are also obtained. A coupled equation is given to theoretically analyze the experimental data. The experimental and theoretical results show that the doubly Q-switched laser has the advantages of a shorter pulse width and higher pulse peak power in contrast with a singly Q-switched laser. OCIS codes: 230.2090, 140.3580, 140.3430, 140.3540.

A doubly Q-switched laser with both an acousto-optic (AO) modulator and a GaAs saturable absorber can obtain a more symmetric and shorter pulse with high pulse peak power, which has been experimentally proved. The key parameters of an optimally coupled doubly Q-switched laser with both an AO modulator and a GaAs saturable absorber are determined, and a group of general curves are generated for what we believe is the first time, when the single-photon absorption (SPA) and two-photon absorption (TPA) processes of GaAs are combined, and the Gaussian spatial distributions of the intracavity photon density and the initial population-inversion density as well as the influence of the AO Q-switch are considered. These key parameters include the optimal normalized coupling parameter, the optimal normalized GaAs saturable absorber parameters, and the normalized parameters of the AO Q-switch, which can maximize the output energy. Meanwhile, the corresponding normalized energy, the normalized peak power, and the normalized pulse width are given. The curves clearly show the dependence of the optimal key parameters on the parameters of the gain medium, the GaAs saturable absorber, the AO Q-switch, and the resonator. Sample calculations for a diode-pumped [Nd.sup.3+]:[YVO.sub.4] laser with both an AO modulator and a GaAs saturable absorber are presented to demonstrate the use of the curves and the relevant formulas. [C] 2007 Optical Society of America OCIS codes: 140.0140, 140.3540, 140.5560.

A doubly Q-switched laser can obtain a shorter pulse with a stable repetition rate and high pulse peak power, which has been experimentally proved. By taking into account the Gaussian spatial distributions of the intracavity photon density and the initial population-inversion density as well as the influence of the acousto-optic (AO) Q switch, we introduce the coupled rate equations for a doubly Q-switched laser with both an AO modulator and a [Cr.sup.4+]-doped saturable absorber. These coupled rate equations are solved numerically. The key parameters of an optimally coupled doubly Q-switched laser are determined based on maximizing the peak power, which include the optimal normalized coupling parameter, the optimal normalized saturable absorber parameters, and the normalized parameters of the AO Q switch. The optimal normalized peak power, the corresponding normalized energy, and the normalized pulse width are also given, and a group of general curves are generated for the first time to our knowledge. The curves can give us a good understanding of the dependence of the optimal key parameters on the parameters of the gain medium, the saturable absorber, the AO Q switch, the resonator, and the spatial distributions of the intracavity photon density. The optimal calculations for a diode-pumped [Nd.sup.3+]:YV[O.sub.4] laser with both an AO modulator and a [Cr.sup.4+]:YAG saturable absorber are presented to demonstrate the use of the curves and the related formulas. OCIS codes: 140.0140, 140.3540, 140.5560.

A diode-pumped passively Q-switched Nd:YV[O.sub.4] green laser with a periodically poled KTP and [Cr.sup.4+]:YAG saturable absorber is realized. The dependences of pulse repetition rate, pulse energy, pulse width, and peak power on incident pump power are measured for the generated green-light pulses. A rate-equation model is introduced to theoretically analyze the results obtained in the experiment, in which the spatial distribution of the intracavity photon density is taken into account. The numerical solutions of the rate equations agree with the experimental results. OCIS codes: 140.3540, 140.3530, 140.3580, 140.3480, 140.3430.

Different techniques to control the pulse width of a diode-pumped passively Q-switched Nd:GdV[O.sub.4]/KTP green laser have been theoretically and experimentally studied. It is shown that, when we vary the positions of the saturable absorber in the laser axis and the pump beam waist in the gain medium, we obtain an efficient means to control the pulse width. The experiments performed on a diode-pumped Nd:GdV[O.sub.4]/KTP green laser passively Q-switched by a [Cr.sub.4+]:YAG saturable absorber are consistent with the theoretical calculations obtained from the rate equation model, in which the intracavity photon density that is assumed to be the Gaussian spatial distribution, the longitudinal variation of the intracavity photon density, and the pump beam spatial distribution are also considered.

By considering the Guassian transversal distribution of intracavity photon density and the longitudinal distribution of photon density along the cavity axis as well as the influence of the turn-off time of the acousto-optic Q switch, we introduce the coupled rate equations of a laser-diode, end-pumped, double Q-switched laser with an acousto-optic modulator and GaAs saturable absorber. In addition the thermal effect of the gain medium is taken into account. These coupled rate equations are solved numerically, and the dependence of pulse width on incident pump power at different pulse repetition rates is obtained for the generated output pulses. It is shown that the pulse duration is obviously shorter in contrast to the actively Q-switched Nd:YV[O.sub.4] laser with an acoustic-optic modulator, and the maximum compression ratio of the pulse width is more than 60%. In the experiment a laser-diode, end-pumped, double Q-switched Nd:YV[O.sub.4] laser with both an acousto-optic modulator and GaAs is realized, and the experimental results agree with the numerical solutions. OCIS codes: 140.3480, 140.3540, 140.3430.

A laser-diode end-pumped actively Q-switched intracavity-doubling laser's rate equations are introduced. Gaussian spatial distributions are assumed and the pump rate, the thermal effect in the gain medium and the change in the photon density along the cavity axis are taken into account in the equations.