Q-switched And Mode-locked Laser Research Articles

Optimization of diode-pumped passively Q-switched mode-locked c-cut Nd:GdVO 4 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:GdVO 4 laser with a GaAs saturable absorber are presented to demonstrate the optimal method applicable.

Diode-pumped passively Q-switched and mode-locked Nd:Lu0.15Y0.85VO4 laser with a GaAs saturable absorber

By using a-cut Nd:Lu0.15Y0.85VO4 mixed crystal as laser gain medium, a diode-pumped passively Q-switched and mode-locked (QML) laser with a GaAs saturable absorber in a Z-type folded cavity is demonstrated for the first time. The Q-switched mode-locked laser pulses with about 90% modulation depth are obtained as long as the pump power reached the oscillation threshold. The repetition rate of the passively Q-switched pulse envelope ranges from 50 to 186 kHz as the pump power increases from 0.915 to 6.520 W. Under an incident pump power of 6.52 W, the QML pulses with the largest average output power of 694 mW, the shortest pulse width of 200 ns and the highest pulse energy of 3.73 μJ are obtained. The mode-locked pulse width inside the Q-switched envelope is estimated to be about 275 ps. The experimental results show that Nd:Lu0.15Y0.85VO4 is a promising mixed crystal for QML laser.

Characteristics of diode-pumped dual-loss-modulated Q-switched and mode-locked Nd:Lu0.15Y0.85VO4 laser

A diode-pumped dual-loss-modulated Q-switched and mode-locked (QML) Nd:Lu0.15Y0.85VO4 laser with acousto-optic (AO) modulator and Cr4+:YAG saturable absorber is presented. The stable QML laser pulse with high peak power and complete modulation depth has been obtained. The QML laser characteristics such as the pulse width, single-pulse energy etc. have been measured for different small-signal transmissions (T0) of Cr4+:YAG, different reflectivity (R) of output coupler and modulation frequencies of the AO modulator (fp). The results show that the pulse energy increases with decreasing fp and increasing T0, while the pulse width decreases with decreasing fp and increasing T0. At fp = 10 kHz, R = 90%, and T0 = 91%, the highest pulse energy and peak power of mode-locked pulses is obtained.

Performance of doubly Q-switched and mode-locked Nd:LuVO<sub>4</sub> laser with acousto-optic modulator and GaAs saturable absorber

A simultaneous Q-switched and mode-locked (QML) Nd:LuVO4 laser with an acousto-optic (AO) modulator and GaAs was presented. By inserting an AO modulator into the laser cavity, the stability of the QML pulses was improved and the pulse width was compressed significantly. The pulse energy and the peak power of mode-locked pulses under the Q-switched envelope had greatly increased. Considering the influences of the turnoff time and the modulation frequency of the AO modulator, a rate equation model for dual-loss modulated QML lasers was given and the numerical solutions of the rate equations were in good agreement with the experimental results.

Optimization of passively Q-switched and mode-locked laser with Cr 4+:YAG saturable absorber

By considering the Gaussian spatial distributions of the intracavity photon density and the initial population-inversion density, the coupled rate equations for a diode-pumped passively Q-switched and mode-locked (QML) laser with Cr 4+:YAG saturable absorber are given. These coupled rate equations are solved numerically and the key parameters of an optimally coupled passively QML laser are determined for the first time. 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. The optimal calculations for a diode-pumped passively QML Nd:GdVO 4 laser with Cr 4+:YAG saturable absorber are presented to demonstrate the numerical simulation applicable.

Passively Q-switched and mode-locked 1.34-μm Nd:YAG laser with V<sup>3+</sup>:YAG saturable absorber

By using vanadium-ion-doped YAG crystal (V3+:YAG) as a saturable absorber, a xenon-lamp-pumped passively Q-switched and mode-locked (QML) Nd:YAG laser at 1.34 µm is realized in a straight cavity. About 90% modulation depth of mode locking of the pulse is obtained. The pulse energy and the pulse width of the QML laser are measured. Under the plane-wave approximation, considering the pump rate and the stimulated radiation lifetime of the active medium as well as the excited-state lifetime of the saturable absorber, modified coupled rate equations are introduced to reconstruct the xenon-lamp-pumped passively QML laser with V3+:YAG. By solving the equations numerically, the theoretical evaluations are found to be in good agreement with the experimental results. The numerical simulation results demonstrate that the model under the plane-wave approximation is accurate enough to describe the dynamical process of xenon-lamp-pumped passively QML laser with V3+:YAG.

Doubly passively Q-switched and mode-locked laser with V3+:YAG and Co:LMA saturable absorbers

By using both V3+:YAG and Co:LMA saturable absorbers, an xenon-lamp-pumped doubly passively Q-switched and mode-locked (QML) Nd:YAG laser at 1.3 μm in a straight cavity is realized for the first time. The modulation depth of QML pulse has nearly reached 100%. The experimental results shows that the doubly passively Q-switched and mode-locked (QML) laser can generate shorter Q-switch envelope pulse with higher average peak power in comparison to the singly passively QML laser with V3+:YAG or Co:LMA saturable absorber.

Diode-pumped doubly Q-switched mode-locked YVO 4/Nd:YVO 4 laser with AO and GaAs saturable absorber

By using both acousto-optic (AO) modulator and GaAs saturable absorber, a diode-pumped doubly Q-switched and mode-locked (QML) YVO 4/Nd:YVO 4 laser is presented. The average output power and the pulse width of the Q-switched envelope have been measured. The Q-switch pulse energy of the doubly QML laser are higher than that only with GaAs. The stability of the QML laser with the dual-loss-modulation is significantly improved if compared to that only with GaAs.The experimental results show that the doubly QML YVO 4/Nd:YVO 4 laser has nearly 80% modulation depth and deeper than that of the singly passively QML pulse. The doubly Q-switched mode-locked pulse inside the Q-switched envelope has a repetition rate of 111 MHz and its pulse width is estimated to be about 700 ps. 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 laser is given and the numerical solutions of the equations are in good agreement with the experimental results.

Passively Q-switched and mode-locked 1.3 μm Nd:YAG laser with Co:LMA saturable absorber

An xenon-lamp-pumped passively Q-switched and mode-locked (QML) Nd:YAG laser with Co:LMA saturable absorber at 1.3 μm is realized in a straight cavity. The modulation depth of mode locking pulse has reached 100%. The pulse energy and the pulse width of QML laser have been measured. The pulse width of the mode-locking laser is estamated to be 940 ps.

Numerical simulation of dual-loss-modulated Q-switched and mode-locked laser with an acousto-optic and Cr^4+:YAGsaturable absorber

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:GdVO(4) laser with AO modulator and Cr(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.

Laser technology

By using mixed crystal Nd:Lu0.15Y0.85VO4 as laser medium, KTP as frequency-doubling crystal, a diode-pumped intracavity-frequency-doubled Q-switched and mode-locked (QML) Nd:Lu0.15Y0.85VO4/KTP green laser with acousto-optic (AO) modulator and central semiconductor saturable absorption mirror (C-SESAM) is realized by using a V-type cavity. The QML laser characteristics such as the pulse width, single-pulse energy, have been measured for different modulation frequencies of the AO modulator. In comparison with the singly passively QML green laser with central SESAM, the doubly QML green laser can generate more stable and shorter pulses with higher peak power. Based on the coupled rate equations for a diode-pumped doubly QML green laser with AO and C-SESAM, in which the saturated absorption mechanism of C-SESAM is considered, the recurrence relation of the relative amplitude of the mode-locking pulses is given and the related numerical simulations are in good agreement with the experimental results.