Study of passive Q-switching for flash-lamp-pumped 1.34-μm Nd:GdVO4 laser

The static laser performance of a-growth Nd:GdVO4 crystal (a-cut, 4 × 4 × 25 (mm)) at 1.34μm pumped by flash-lamp is investigated with different transmissions of output couplers. With the output coupler transmission of T = 30%, the static output energy of 148 mJ is obtained when the pump energy is 35.2 J,and the corresponding electric-optical conversion efficiency is 0.42%. The Q-switched output of lasers with the output wavelength ranging from 1.3 to 1.6 μm can be realized by using Co2+ :LaMgAl11O19 (Co:LMA)as saturable absorber. A flash-lamp-pumped, passively Q-switched Nd:GdVO4 laser with Co:LMA as saturable absorber is demonstrated in plano-concave laser cavity. With the cavity length of 16.3 cm and pump energy of 19.8 J, the single-pulse output energy, pulse width, and peak power are obtained to be 4m J, 80 ns, and 5 × 104 W, respectively.     

Passively Q-switched laser operation in a composite Nd:YVO4/Nd:YVO4/Nd:YVO4 crystal with a GaAs saturable absorber

By using a piece of GaAs wafer as the saturable absorber, the performance of the passively Q-switched composite Nd:YVO₄ laser with different output couplers has been demonstrated for the first time as far as we know. The largest continuous wave output power of 1.52 W is obtained at the incident pump power of 5.31 W, giving an optical conversion efficiency of 28.7% and a slope efficiency of 30.2%. The shortest pulse width of 11 ns, the largest single-pulse energy of 2.49 μJ and the highest peak power of 190 W are also obtained.     

A diode-pumped passively Q-switched Nd:GdVO4 laser with a GaAs saturable absorption

We have demonstrated a passively Q-switched operation of Nd:GdVO₄ laser in which a GaAs crystal is used as the saturable absorber for the first time as far as we know. A maximum average output power of 1.64 W was obtained at an incident pump power of 12 W, the corresponding optical conversion efficiency and peak power were 13.7% and 116.8 W, respectively. The maximum peak energy obtained in the experiment by 50% transmission couple was 19 μJ.     

Passively Q-switched 1.32-μm Nd:YAG laser with a V:YAG saturable absorber

By using a new saturable absorber V³⁺:YAG, a flash-lamp-pumped passively Q-switched Nd:YAG laser at 1.32 μm has been realized. The single-pulse energy and the pulse width of the output laser versus the pump energy are measured. With a cavity length of 440 mm and a pump energy of 43.4 J, the obtained single-pulse output energy and pulse width are 10 mJ and 86.9 ns, respectively, corresponding to a peak power of 115 kW.     

Diode-pumped passively Q-switched and mode-locked Nd:Lu<Subscript>0.15</Subscript>Y<Subscript>0.85</Subscript>VO<Subscript>4</Subscript> laser with a GaAs saturable absorber

By using a-cut Nd:Lu_0.15Y_0.85VO₄ 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:Lu_0.15Y_0.85VO₄ is a promising mixed crystal for QML laser.     

微型化LD泵浦Er~(3+),Yb~(3+)共掺磷酸盐玻璃被动调Q激光器

报道了一种主要应用于激光测距的微型化激光二极管泵浦Er3+/Yb3+共掺磷酸盐玻璃被动调Q激光器。采用中心波长940nm的二极管作为泵浦源,Er3+/Yb3+共掺磷酸盐玻璃作为增益介质,Co2+:MgAl2O4作为被动调Q晶体,通过优化增益介质和被动调Q晶体参数,获得了最佳的增益介质长度和被动调Q晶体初始透过率。当泵浦能量14mJ,重复频率10Hz,泵浦脉宽5ms时,获得了单脉冲能量480μJ,脉宽5ns,峰值功率大于20kW的激光输出,激光光束质量因子为1.2。     

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.     

Co:LaMgAl11O19 saturable absorber Q-switch for a 1.319 μm Nd:YAG laser

Passively Q-switched output of a flashlamp-pumped 1.319 μm Nd:YAG laser is realized by using Co²⁺:LaMgAl₁₁O₁₉ (Co:LMA) as saturable absorber. When initial transmission of the saturable absorber T₀ is 78%, a Q-switched output pulse with pulse width (FWHM) 44.8 ns and pulse energy 17.4 mJ is obtained, corresponding to 19.3% of the free-running energy under the equal pumping energy of 45.4 J. The experimental results show that the higher T₀ will result in a lower pumping threshold of the laser, but lower T₀ can make the laser generate pulses with higher single-pulse energy, narrower pulse width, and accordingly higher peak power.     

Laser–diode-pumped passively Q-switched Nd:NaY(WO4)2 laser with GaAs saturable absorber

A laser–diode-pumped passively Q-switched new type crystal Nd³⁺:NaY(WO₄)₂ (known as Nd:NYW) laser with GaAs semiconductor saturable absorber has been realized. The dependence of pulse repetition rate, pulse energy, pulse width, and peak power on pump power for different output coupler reflectivities are measured. The coupled rate equations are used to simulate the Q-switched process of laser, and the numerical solutions agree with the experimental results.     

Diode-pumped doubly Q-switched Nd:LuVO4 laser with AO modulator and GaAs saturable absorber

A diode-pumped doubly Q-switched Nd:LuVO₄ laser with an acousto-optic (AO) modulator and GaAs saturable absorber has been realized. The pulse profile of the doubly Q-switched Nd:LuVO₄ laser has an almost absolutely symmetric shape. The dependences of pulse width, single-pulse energy and peak power on the incident pump power under different AO repetition rates are measured. By considering the transverse Gaussian distribution of the intracavity photon density and the longitudinal distribution of photon density along the cavity axis, the coupled rate equations of the laser are given. These coupled rate equations are solved numerically and the theoretical results are in agreement with the experimental results.     

Diode-pumped passively Q-switched Nd:GGG crystal with GaAs saturable absorber

We have experimentally studied the passive Q-switching performance of a diode-pumped Nd-doped gadolinium gallium garnet (Nd:GGG) laser with a GaAs saturable absorber. Stable Q-switched pulses as short as 9 ns with a repetition rate of 196.1 kHz have been obtained with an appropriately coated GaAs wafer used as the output coupler. At 12.44 W of the absorbed pump power, an average output power of 1.03 W has been obtained and the corresponding pulse energy and peak power are 5.25 μJ and 0.58 kW, respectively.     

Multi-watt Q-switched Nd:YVO_4 laser with GaAs output coupler

A passively Q-switched operation of a diode-pumped Nd.YVO_4 laser is demonstrated, in which a GaAsfilm is used as the saturable absorber as well as the output coupler. At the pump power of 10 W, a stablefundamental-mode average power output of 2.11 W was obtained with a pulse duration of 140 ns, pulseenergy of 76 μJ and pulse repetition rate of 28 kHz. A theoretical analysis that describes the passiveQ-switching dynamics of GaAs is presented.     

High repetition rate passively Q-switched diode-pumped Nd:YVO4 laser

We demonstrated an efficient and compact, diode-pumped passively Q-switched Nd:YVO₄ laser operation at 1.064 μm wavelength with high repetition rate, using Cr⁴⁺:YAG as saturable absorber, formed with a simple flat–flat resonator. The maximum CW output power of 4.05 W was obtained at the incident pump power of 8 W. For Q-switched operation, the maximum average output power was measured to be 1.4 W with the corresponding repetition rate of 200 kHz, the pulse width of 60 ns when the initial transmission of Cr⁴⁺:YAG crystal was 85%. The shortest pulse width of 12 ns, the largest pulse energy of 36 μJ and the highest peak power of 3 kW were obtained when the Cr⁴⁺:YAG crystal with an initial transmission of 60% was used.     

Diode-pumped doubly Q-switched mode-locked YVO4/Nd:YVO4 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) YVO₄/Nd:YVO₄ 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 YVO₄/Nd:YVO₄ 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.     

Doubly Q-switched intracavity-frequency-doubled c-cut Nd:GdVO4/KTP green laser with AO and GaAs

By simultaneously using both active and passive Q-switches in the same cavity, a diode-pumped doubly Q-switched intracavity-frequency-doubled c-cut Nd:GdVO₄/KTP green laser with acoustic-optic (AO) modulator and GaAs semiconductor saturable absorber is realized. A comparison between c-cut and a-cut Nd:GdVO₄ crystals shows that the doubly Q-switched c-cut Nd:GdVO₄/KTP green laser can generate narrower pulse and higher peak power when the incident pump power is higher than 4.4 W. In addition, the doubly Q-switched c-cut Nd:GdVO₄/KTP green laser can generate more symmetric and shorter pulse in comparison with singly AO- or GaAs-Q-switched laser. The coupled rate equations are used to simulate the process of these lasers.     

Optimization of GaAs semiconductor saturable absorber Q-switched lasers

The expressions of pulse characteristics such as output energy, peak power, and pulse width are obtained by solving the coupled rate equations describing the operation of GaAs semiconductor saturable absorber Q-switched lasers. The key parameters of an optimally coupled GaAs saturable absorber Q-switched laser are determined and several design curves are generated from these expressions for the first time. These key parameters include the optimal normalized coupling parameters and the optimal normalized saturable absorber parameters that maximize the output energy or maximize the peak power, and the corresponding normalized energy, normalized peak power, and normalized pulse width. Using the expressions and design curves, one can predict the pulse characteristics and perform the design of an optimally coupled GaAs saturable absorber Q-switched laser.     

A laser-diode end-pumped passively Q-switched intracavity doubling Nd:GdVO<Subscript>4</Subscript>/KTP red laser with V<Superscript>3+</Superscript>:YAG saturable absorber

Using a V³⁺:YAG saturable absorber, we realize the running of a laser-diode end-pumped passively Q-switched intracavity-frequency-doubling Nd:GdVO₄/KTP red laser. Under the absorbed pump power of 9.45 W and with V³⁺:YAG initial transmission T ₀ = 94%, the obtained average output power and pulse width were 610 mW and 15.09 ns with the repetition rate of 12.2 kHz, corresponding to the single pulse energy 50 μJ and the pulse peak power 3.34 kW.     

Diode-pumped passively Q-switched mode-locked Nd:YLF laser with uncoated GaAs saturable absorber

We have demonstrated passively Q-switched mode-locked all-solid-state Nd:YLF laser with an uncoated GaAs wafer as saturable absorber and output mirror simultaneously. Q-switched mode-locking pulses laser with about 100% modulation depth were obtained. The average output power is 890 mW at the incident pump power of 5.76 W, corresponding to an optical slop efficiency of 20%. The temporal duration of mode-locked pulses was about 21 ps. At the Q-switched repetition rate of 30 kHz, the energy and peak power of a single pulse near the maximum of the Q-switched envelope was estimated to be about 1.6 μJ and 76 kW.     

Passively Q-switched laser operation in a composite Nd:YVO<Subscript>4</Subscript>/Nd:YVO<Subscript>4</Subscript>/Nd:YVO<Subscript>4</Subscript> crystal with a single-walled carbon nanotube saturable absorber

By using a piece of single-walled carbon nanotube saturable absorber, the performance of the passively Q-switched composite Nd:YVO₄ laser has been demonstrated for the first time. The maximum average output power and the shortest pulse width are 1220 mW and 103 ns at the incident pump power of 5.04 W for a 10% transmission of the output coupler. The highest pulse repetition rate of 415.6 kHz and the largest single-pulse energy of 2.94 μJ are also obtained. The composite Nd:YVO₄ crystal has more excellent laser performance than the normal Nd:YVO₄ crystal at 1064 nm.     

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.