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.     

Passively Q-switched Nd:GdVO4 laser with In0.25Ga0.75As being an output coupler

We report a diode-end-pumped passively Q-switched Nd:GdVO₄ laser operating at 1.06 μm with In_0.25Ga_0.75As being the saturable absorber as well as an output coupler. Q-switched pulses with a pulse duration of 20 ns, pulse energy 4.2 μJ and pulse repetition rate 200 kHz were produced, corresponding to peak power of 210 W.     

Q-switched and mode-locked diode-pumped Nd:YVO4 laser with an intracavity composite semiconductor saturable absorber

We have demonstrated a passively Q-switched and mode-locked Nd:YVO₄ laser with an intracavity composite semiconductor saturable absorber (ICSSA). Stable Q-switched and mode-locked pulses with Q-switched envelope pulse duration of 180 ns and pulse repetition rate of 72 KHz have been obtained. The maximum average output power was 1.45 W at 8 W incident pump power. The repetition rate of the mode-locked pulses inside the Q-switched envelope was 154 MHz. Experimental results revealed that this ICSSA was suitable for Q-switched and mode-locked solid-state lasers.     

Stable Q-switch mode-locking of Nd:YVO<Subscript>4</Subscript> lasers with a semiconductor saturable absorber

This paper reports on a passively mode-locked and Q-switched Nd:YVO₄ laser generating picosecond pulses with an average output power exceeding 7 W. In a first step Q-switch mode-locking was obtained by self Q-switching of a mode-locked oscillator with appropriate cavity design, pump power and output coupling. In a second system the Q-switching was actively controlled and stabilized by modulating the resonator internal losses with an acousto-optic modulator. In the Q-switch mode-locking operation the laser provided 12.8 ps long mode-locked pulses with a repetition rate of 80 MHz. The repetition rate of the Q-switch envelope was 185 kHz. The maximum pulse energy of a single ps pulse was 0.55 μJ which is 5.5 times the pulse energy measured for cw mode locking. The total energy of the pulses within the Q-switch envelope was 42 μJ. PACS  42.55.Xi; 42.60.Fc; 42.60.Gd     

The influence of thermal lens effect on pulse repetition rate in diode-pumped passively Q-switched Nd:GdVO4/V:YAG laser

The influence of thermal lens effect on pulse repetition rate in diode-pumped Nd:GdVO₄ 1.34 μm laser has been demonstrated. The repetition rate first increased, then reduced with augment of the pump power, for V:YAG with initial transmission (T₀) of 96%. The maximum repetition rate was 70 kHz, obtained at the pump power of 6.78 W. The best output laser characteristics—the pulse width of 39.2 ns, the peak power of 2.5 kW and the single pulse energy of 102 μJ—were obtained by V:YAG of T₀=89%. With the Gaussian spatial distribution of intracavity photon density being considered, the rate equations were solved numerically and the theoretical calculations agreed with the experimental results.     

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.     

13-W picosecond Nd:GdVO4 regenerative amplifier with 200-kHz repetition rate

We report a diode-pumped picosecond Nd:GdVO₄ regenerative amplifier system designed for micro-machining applications. Nd:GdVO₄ was chosen as gain material because it offers – in comparison to the commonly used Nd:YVO₄ – improved thermal properties and a larger gain bandwidth. At the maximum repetition rate of 200 kHz, the system generated 6.8-ps-long pulses with a pulse energy of 65 μJ, which corresponds to an average output power of 13 W. At 100 kHz, the pulse energy increased to 123 μJ, whereas the average power of 12.3 W remained almost identical. The broadening of the pulses due to gain narrowing was investigated in dependence on the number of cavity round trips and on the repetition rate. At 200 kHz, the injected 5.3-ps-long pulses broadened slightly to about 6.8 ps.     

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     

LD-pumped actively Q-switched Tm,Ho:YLF laser at room temperature

We have investigated acoustic-optical Q-switched Tm,Ho:YLF laser end-pumped by a laser-diode. At room temperature, a 2.067 μm wavelength pulsed output is realized. Average output power, single pulse energy and pulse-width are measured at different incident pump powers and pulse repetition frequencies. When the incident pump power is 2.8 W, a maximum average output power of 189 mW is obtained at the repetition frequency of 9 kHz, and this corresponds to an optical conversion efficiency of 6.8%. The maximum single pulse energy of 65μJ, the shortest pulse-width with full-width at half-maximum (FWHM) of 138 ns and the maximum peak power of 470 W are obtained at the pulse repetition frequency of 1 kHz.     

High-power high-repetition-rate acousto-optically Q-switched 1342 nm laser

A high-power high-repetition-rate acousto-optically Q-switched 1342 nm laser with double Nd:YVO₄ crystals pumped by fiber-coupled laser diodes is presented. The highest output power of 13.7 W was achieved with a total of 42 W pumping power in cw operation, the slope efficiency was measured as 36%, and the optical efficiency was better than 32%. In Q-switchedoperation, the highest pulse repetition rate of 100 kHz was obtained. At 50 kHz repetition rate, the laser exported 11.2 W average output power, with 60 ns average pulse width, ∼5% width stability (RMS) and ∼8% peak-power stability (RMS). At 10 kHz repetition rate, the highest average output power was measured as 6.3 W, single pulse energy was calculated as 0.63 mJ, with pulse width of 19 ns and peak-power higher than 30 kW. Combining the experimental results, we analyze and discuss some problems concerning Nd:YVO₄ crystal working at 1,342 nm wavelength. PACS 42.55.-f; 42.55.Xi; 42.60.Gd     

The characteristics of diode-pumped acousto-optic Yb:Y2Ca3B4O12 laser for Q-switching and Q-switched mode-locking

Q-switching and Q-switched mode-locked Yb:Y₂Ca₃B₄O₁₂ lasers with an acousto-optic switch are demonstrated. In the Q-switching case, an average output power of 530 mW is obtained at the pulse repetition rate of 10.0 kHz under an absorbed pump power of 6.1 W. The minimum pulse width is 79 ns at the repetition rate of 1.7 kHz. The pulse energy and peak energy are calculated to be 231 μJ and 2.03 kW, respectively. In the Q-switched mode-locking case, the average output power of 64 mW with a mode-locked pulse repetition rate of 118 MHz and Q-switched pulse energy of 48 μJ is generated under the absorbed pump power of 6.1 W.     

High-average-power and high-conversion-efficiency continuous wave mode-locked Nd:YVO4 laser with a semiconductor absorber mirror

A high-power continuous wave (cw) mode-locked Nd:YVO₄ solid-state laser was demonstrated by use of a semiconductor absorber mirror (SAM). The maximum average output power was 8.1 W and the optic-to-optic conversion efficiency was about 41%. At the maximum incident pump power, the pulse width was about 8.6 ps and the repetition rate was 130 MHz. Experimental results indicated that this absorber was suitable for high power mode-locked solid-state lasers.     

Passive Q-switching performance with Co:LMA crystal in a diode-pumped Nd:LuVO<Subscript>4</Subscript> laser

A diode-pumped passively Q-switched Nd:LuVO₄ 1.34 μm laser using Co:LMA saturable absorber was successfully demonstrated. The average output power, pulse width, repetition rate of a-cut and c-cut Nd:LuVO₄ lasers were studied with different output couplers. The maximum average output power of 164 mW was obtained at the pump power of 10.3 W and the narrowest pulse width of 168 ns was achieved at repetition rate of 457 kHz under pump power of 8.59 W in a-cut Nd:LuVO₄ laser with T = 8%.     

Performance of actively Q-switched Nd:LiLuF<Subscript>4</Subscript> crystal end-pumped by a 792 nm laser diode

An efficient laser diode end-pumped continuous-wave (CW) and AO Q-switched laser of Nd:LiLuF₄ crystal with dual central wavelengths of 1053.1 and 1054.7 nm is reported for the first time. The maximum CW output power of 6.22 W was obtained at absorbed pump power of ∼14.6 W with the output transmission of 2%. The optical conversion efficiency is ∼43%, corresponding to a slope efficiency of about 48% with respect to the absorbed pump. For the Q-switched operation, the shortest pulse width of 17 ns was obtained at the pulse repetition frequency (PRF) of 0.5 kHz, resulting in a pulse energy of 2.24 mJ and peak power of 131.8 kW.     

LD-pumped passively Q-switched Nd:GdVO<Subscript>4</Subscript> laser at 1342 nm with high initial transmission V:YAG saturable absorber

We have realized, for the first time to our knowledge, the passive Q-switching operation of an LD-pumped Nd:GdVO₄ laser at 1342 nm with V:YAG saturable absorber of initial transmission as high as 96%. This laser is investigated under different transmissions of the output coupler. The dependences of average output power, pulse width, pulse repetition rate, single-pulse energy and peak power on incident pump power are also measured. The shortest pulse width of 80 ns, the maximum single-pulse energy of 19.5 μJ and the highest peak power of 244 W are obtained with the output coupler of T = 15% and the pump power of 7.93 W. We find a special experimental phenomenon that the pulse repetition rate begins to drop after reaching the peak with the increase of the pump power. This phenomenon is analyzed and the theoretical calculations are consistent with the experimental results.     

Efficient fourth harmonic UV generation of passively Q-switched Nd:GdVO4/Cr:YAG lasers

A coherent UV passively Q-switched diode pumped Nd:GdVO₄ laser source is proposed. During pumping of the β-BBO crystal a stable light with power 0.6 W with wavelength 532 nm and pulse duration 9 ns at frequency repetition 16 kHz was applied. The output UV light has a power about 79 mW at wavelength 266 nm during diode-pumping with 8 W incident light.     

880 nm LD pumped passive Q-switched and mode-locked Nd:YVO<Subscript>4</Subscript> laser using a single-walled carbon nanotube saturable absorber

We report a 880 nm LD pumped passive Q-switched and mode-locked Nd:YVO₄ laser using a single-walled carbon nanotube saturable absorber (SWCNT-SA). At the pump power of 7.78 W, the average out-put power of 330 mW of Q-switched and mode-locked laser with optical conversion efficiency of 4.2% was generated. The repetition rate and pulse width of the Q-switched envelope were 33 kHz and 5.6 μs, respectively. The repetition rate and pulse energy of the mode-locked pulse within the Q-switched envelope were 80 MHz and 4.1 nJ, respectively.     

Cavity-dumped electro-optical Q-switched Nd:GdVO4 laser with high repetition rate

We reported a cavity-dumped operation of electro-optical Q-switched Nd:GdVO₄ laser at high repetition rates for the first time. A constant 5.5 ns pulse duration was realized. The maximum average output power was 5.1 W at the highest repetition rate of 50 kHz, corresponding to a peak power of 18.5 kW.     

Diode-pumped passively Q-switched Nd:GdVO4 laser at 1342 nm with V:YAG saturable absorber

We have demonstrated an efficient diode-pumped passively Q-switched Nd:GdVO₄ laser working at 1342 nm by using an uncoated V³⁺:YAG crystal as the saturable absorber, in which both a-cut and c-cut Nd:GdVO₄ crystals are employed. At the maximum absorbed pump power of 9.45 W, the maximum average output power can reach 519 mW and 441 mW corresponding to the output coupler with different transmission of 3% and 10% by using an a-cut Nd:GdVO₄ crystal at 1342 nm, while the shortest pulse duration could be as low as 21.7 ns and 22.3 ns with the repetition rate of 48.41 kHz and 53.25 kHz by using a c-cut Nd:GdVO₄ crystal, corresponding to the output coupler with different transmission of 3% and 10% at 1342 nm, and the single Q-switched pulse energy are 6.67 uJ and 7.06 uJ, the pulse peak power are 307 W and 316 W, respectively. The experimental results show that c-cut Nd:GdVO₄ laser can generate shorter pulse with higher peak power in comparison with a-cut one.     

High-pulse-stability double-end continuous-grown YVO<Subscript>4</Subscript>/Nd:YVO<Subscript>4</Subscript>/YVO<Subscript>4</Subscript> acousto-optically Q-switched laser at high repetition rates

High pulse amplitude stability of 0.62% (rms) is achieved at 60 kHz repetition rate in fundamental mode with double-end continuous-grown YVO₄/Nd:YVO₄/YVO₄ composite crystal. The average output power and pulse peak power are 32.9 W and 27.7 kW, respectively, with 19.8 ns pulse width and 548 μJ pulse energy. The pulse amplitude stability is investigated experimentally. The stability gets improved with the decrease of repetition rate and output transmission. From theoretical analysis, the reason of pulse instability at high repetition rates is that the initial population inversion doesn’t saturate and the final population inversion doesn’t approach zero. With the decrease of repetition rate and output transmission, the final population inversion decreases and the interaction between two adjacent pulse periods is weakened. Therefore, pulse stability improves.