Theoretical and experimental studies on passively Q-switched KTiOAsO4 optical parametric oscillator

A passively Q-switched intracavity optical parametric oscillator based on KTiOAsO₄ (KTA) crystal is studied theoretically and experimentally. The rate-equation-based theoretical model is established to describe the time evolutions of the population inversion density of the laser crystal, ground-state population density of the saturable absorber, fundamental photon density, signal photon density and the idler photon density. In the experiment, a laser diode-end pumped, passively Q-switched Nd:YAG/KTA IOPO with a Cr⁴⁺:YAG crystal as the saturable absorber is realized to verify this model. The characteristics including the output power, the pulse repetition rate, the pulse width and the beam quality were investigated for this OPO. The experimental results for the output power and the repetition rate agree with the theory well. And both results show that with same pumping level the idler pulse width is shorter than the signal one.     

Analysis of a laser-diode end-pumped passively Q-switched Nd:GdVO4 laser with V3+:YAG saturable absorber

By considering both the transversal and longitudinal Gaussian spatial distribution of the intracavity photon density, a couple of rate equations describing a laser-diode end-pumped passively Q-switched Nd:GdVO₄ laser with V³⁺:YAG saturable absorber have been proposed. Solving these space-dependent rate equations numerically, we obtain the dependences of pulse width, pulse repetition rate, single-pulse energy and peak power on pump power. In the experiment, a laser-diode end-pumped Nd:GdVO₄ laser passively Q-switched by a V³⁺:YAG saturable absorber has been realized, and the experimental results are consistent with the theoretical calculations.     

High-Pulse-Energy Passively <Emphasis Type="Italic">Q</Emphasis>-Switched 1,123 nm Laser with a Nd:GdYAG Mixed Garnet as Laser Medium

We demonstrate a diode-pumped passively Q-switched Nd:GdYAG mixed garnet laser at 1,123 nm. A Cr⁴⁺:YAG crystal with an initial transmission of 97% is used as the saturable absorber. The maximum average output power is 1.05 W at an absorbed pumping power of 8.12 W. A single-pulse energy can reach up to 78.9 μJ, with a corresponding pulse repetition rate of 13.3 kHz.     

A Single -Longitudinal-Mode Nd:Ce:YAG <Emphasis Type="Italic">Q</Emphasis>-Switched Laser Based on a Three-Plan Resonant Reflector

We present an efficient and compact passively Q-switched flash-lamp-pumped Nd:Ce:YAG singlelongitudinal-mode (SLM) laser system. With Cr⁴⁺:YAG as a saturable absorber, we design a three-plan resonant reflector for generating smooth SLM Q-switched pulses. We provide a theoretical calculation and optimization of the resonant reflector for improving the longitudinal-mode selection ability. We obtain a stable SLM output with a single-pulse energy of 10 mJ and a pulse width of 10.7 ns at 10 Hz. The near-diffraction-limited beam-quality parameter M² is less than 1.5. The system can operate with a repetition rate from 1 to 10 Hz. We achieve the stable laser operation with less than 3% fluctuation of the pulse energy within 10,000 shots.     

High Average Power, Compact Passively Q-Switched 532 nm Green Laser on Nd:YAG/Cr4+:YAG Composite Crystal

We design a passively Q-switched intracavity frequency-doubled 532 nm laser using Nd:YAG/Cr⁴⁺:YAG composite crystal and type II phase matching KTP crystal. Under 13.97 W pump power, the average output power of the laser elaborated is up to 681 mW, with 200 ns pulse width and 9.1 kHz pulse repetition rate.     

Diode-pumped passively Q-switched YAG/Yb:YAG laser with Cr4+:YAG as a saturable absorber

We design an efficient passively Q-switched laser using a composite YAG/Yb:YAG crystal as the laser gain medium and a Cr⁴⁺:YAG crystal as a saturable absorber. We obtain an average output power of 1.81 W in 1030 nm laser at an absorbed pump power of 4.8 W, corresponding to an optical-to-optical efficiency of 37.7% and a slope efficiency of 47.3%. The pulsed laser has a repetition rate of about 28.6 kHz and a pulse width of 15.8 ns, with the highest peak power of 4 kW. In addition, using a LBO as the intracavity frequency doubler, we obtain a maximum power of 246 mW in 515 nm pulsed laser at an absorbed pump power of 3.8 W.     

Passively Q-switched Nd:LuVO4 laser using Cr:YAG as saturable absorber

A passively Q-switched all solid-state Nd:LuVO₄ 1.06 μm laser was demonstrated by using Cr⁴⁺:YAG as saturable absorber. The characteristics of average output power, pulse width, repetition rate, pulse energy, and peak power were studied with different output couplings and initial transmission of saturable absorbers. When output coupling with the transmission of 20% was used, the shortest pulse width of 16 ns at the repetition rate of 12.5 kHz was obtained, which results in the pulse energy of 71 μJ and peak power of 4.43 kW with the initial transmission of 70% of Cr⁴⁺:YAG crystal.     

Doubly <Emphasis Type="Italic">Q</Emphasis>-Switched Nd:YAG Ceramic Laser

Using simultaneously both an acousto-optic (AO) modulator and a Cr⁴⁺:YAG saturable absorber in the cavity, we demonstrate for the first time the performance of a diode-pumped doubly Q-switched Nd:YAG ceramic laser. In contrast to purely acousto-optic Q-switched laser, this doubly Q-switched laser can generate shorter and more symmetric pulses. At an absorbed pump power of 10 W and a repetition rate of 20 kHz, the pulse width is compressed to 30 and 25 ns, respectively.     

High-Power passively Q-switched 532 nm green laser by using Nd:YAG/Cr4+:YAG composite crystal

This paper reported a passively Q-switched 532 nm green laser of LD pumped V cavity structure by using Nd:YAG/Cr⁴⁺:YAG composite crystal and the type II phase matching KTP crystal. Under 19.4 W pump power, the average power of the laser pulse up to 1.83 W, with the pulse width of 93.2 ns and repetition frequency of 9.1 kHz.     

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.     

Passive Q-switching of a laser-diode-pumped intracavity-frequency-doubling Nd:Nd<Superscript>3+</Superscript>:NaY(WO<Subscript>4</Subscript>)<Subscript>2</Subscript>/KTP laser with Cr<Superscript>4+</Superscript>:YAG saturable absorber

Nd³⁺:NaY(WO₄)₂, known as Nd:NYW, is a new type crystal. By using laser-diode as pump source, a passive Q-switching of intracavity-frequency-doubling Nd:NYW/KTP laser has been realized with Cr⁴⁺:YAG saturable absorber. The dependence of pulse repetition rate, pulse energy, pulse width, and peak power on incident pump power for different small-signal transmissions of Cr⁴⁺:YAG 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 Q-switched Nd:Y<Subscript>0.5</Subscript>Lu<Subscript>0.5</Subscript>VO<Subscript>4</Subscript> laser double-modulated with an acousto-optic modulator and Cr<Superscript>4+</Superscript>:YAG saturable absorber

A diode pumped Nd:Y_0.5Lu_0.5VO₄ pulse laser modulated with an acousto-optic (AO) Q-switcher and Cr⁴⁺:YAG saturable absorber is first demonstrated in this paper. The laser is shown to generate shorter pulse width than AO Q-switched laser alone, and have a higher peak power and single pulse energy than passively Q-switched laser with only Cr⁴⁺:YAG. A laser pulse width of 6.16 ns and a peak power of about 43.83 kW are achieved at the incident pumping power of 14.09 W.     

Improvement of laser characteristics for diode-pumped passively Q-switched and mode-locked Nd:Lu0.15Y0.85VO4 laser by AO modulator

The hybrid Q-switched and mode-locked (QML) operation of Nd:Lu_0.15Y_0.85VO₄ crystal at 1.34 ??m with V:YAG saturable absorber and acousto-optic (AO) modulator has been realized. The laser characteristics are distinctly improved by the hybrid QML if compared to those with the single V:YAG QML. At the pump power of 5.04 W, the Q-switched pulse energy is enlarged to 5.6 times and the Q-switched pulse width is shortened to 40% by the AO modulator in contrast to those of the single passively QML.     

Passively Q-switched intracavity frequency-doubled Nd:LuVO<Subscript>4</Subscript>/LBO green laser with a Cr<Superscript>4+</Superscript>:YAG saturable absorber

This work presents experimental results concerning a passively Q-switched intracavity frequencydoubled Nd:LuVO₄/LBO green laser with a Cr⁴⁺:YAG saturable absorber operated at the wavelength of 0.53 μm. A maximal output power of 1.28 W was obtained at a pump power of 16.34 W, and peak power, pulse width as well as repetition frequency were 1.48 kW, 41 ns and 21 kHz, respectively.     

An Intracavity-Triggered Passively-Switched Nd:YVO<Subscript>4</Subscript> Laser

We demonstrate an intracavity-triggered passively Q-switched Nd:YVO₄ laser within a diode-end-pumped configuration. We employ a Cr⁴⁺:YAG saturable absorber as the passive Q switch and an Nd:LiYF₄ (YLF) laser as the laser triggering of the Q-switched laser. Since we use the same Cr⁴⁺:YAG crystal and output coupler with the Nd:YVO₄ laser, the Cr⁴⁺:YAG Q switch is triggered inside the Nd:YLF laser cavity. As a result, the timing jitter in standard deviation of Nd:YVO₄ laser can be reduced to 16 ns.     

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.     

Compact passively Q-switched green laser with periodically poled MgO:LiNbO<Subscript>3</Subscript>

Passively Q-switched green output with Cr⁴⁺:YAG as saturable absorber and PPMgLN as the frequency doubling crystal was realized in a compact diode end-pumped Nd:YVO₄ laser. The green light output power, pulse width, pulse repetition rate, pulse energy and peak power with three Cr⁴⁺:YAG of different initial transmissions were investigated. The maximum average output power was 1.2 W at the pump power of 4.0 W and the maximum conversion efficiency was 30% with the Cr⁴⁺:YAG of 90% initial transmission. The maximum pulse energy and minimum pulse width were 10.9 μJ and 12 ns with the Cr⁴⁺:YAG of 75% initial transmission.     

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.     

Diode end-pumped passively Q-switched Nd:YAG ceramic laser with Cr4+:YAG saturable absorber

We report on a diode end-pumped passively Q-switched Nd:YAG ceramic laser. By using a Cr⁴⁺:YAG single crystal with an 80% initial transmission as the saturable absorber, stable Q-switched pulses with a 126-μJ pulse energy, a 12-ns pulse width, and an 8.4-kHz pulse repetition rate have been obtained. The Q-switching performance of the laser under different saturable absorption strengths and output couplings was experimentally investigated.     

A Novel 1,066 nm Nd:Gd<Subscript>0<Emphasis Type="Italic">.</Emphasis>69</Subscript>Y<Subscript>0<Emphasis Type="Italic">.</Emphasis>3</Subscript>NbO<Subscript>4</Subscript> Passively <Emphasis Type="Italic">Q</Emphasis>-Switched Pulse-Burst Laser

We demonstrate for the first time a Cr⁴⁺:YAG passively Q-switched 1066 nm pulse-burst laser under 879 nm direct pump with a novel Nd:Gd_0.69Y_0.3NbO₄ crystal. The output laser characteristics with different pump repetition rates and different Cr⁴⁺:YAG initial transmission are studied. Without the Cr⁴⁺:YAG, we obtain a maximum output energy of 2.55 mJ at an absorbed pump energy of 5.79 mJ with the highest 48% slope efficiency. The pulse-burst laser contains a maximum of 7 pulses for a Cr⁴⁺:YAG initial transmission of 55% and a pump repetition rate of 1 kHz. The single-pulse energy and narrowest pulse width reach 160 μJ and 5.5 ns at 38.2 kHz, with a peak power of 32 kW.