Intracavity frequency doubling of an active Q-switched Nd:YAG laser with 2.25 W output power at 473 nm

An active Q-switched diode-end-pumped Nd:YAG laser is reported with 2.9 W output power on the ⁴F_3/2 → ⁴I_9/2 transitions at a pump power of 24 W. With intracavity frequency doubling using a 20-mm-long LBO, a maximum blue output power of 2.25 W is achieved at a repetition rate of 23 kHz. The conversion efficiency from the corresponding Q-switched fundamental output to blue output is 96%. The peak power of the Q-switched blue pulse is up to 610 W with 160 ns pulse width. The fluctuation of the blue output power is less than 4.0% at the maximum output power.     

Continuous-wave and passively Q-switched laser performance of a disordered Nd:GYSGG crystal

The performance of continuous wave (CW) and passively Q-switched Nd:GYSGG lasers was investigated for the first time. The CW output powers of 4.2 W with dual wavelength of 1058.4 nm and 1061.5 nm were obtained under the diode pump power of 17 W with slope efficiencies of 26%. By using Cr⁴⁺:YAG wafer as saturable absorber, Q-switching operation was performed and the short pulse with pulse width of 6.6 ns was obtained with the peak power of 9.97 kW.     

High efficiency TEM00 mode, diode-pumped, conduction-cooled, Nd:YAG zig-zag slab laser

We report a compact, conduction-cooled, highly efficient, continuous wave (CW) Nd:YAG slab laser in diode-side-pumped geometry. To achieve high efficiency, a novel laser head for Nd:YAG slab has been developed. For an absorbed pump power of 27.6 W, maximum output power of 10.4 W in multimode and 8.2 W in near-diffraction-limited beam quality has been obtained. Slope and optical-to-optical conversion efficiencies are 45.3% and 37.7% in multimode with beam quality factors (M²) in x and y directions equal to 32 and 8, respectively. TEM₀₀ mode operation was achieved in a hybrid resonator with slope and optical-to-optical conversion efficiencies of 43.2% and 29.7%, respectively. Beam quality factors in x and y directions are ?1.5 and ?1.6 for the whole output power range. The laser radiation was linearly polarized and polarization contrast ratios are >1200:1 in the multimode and 1800:1 in the TEM₀₀ mode operation. In passive Q-switching with Cr⁴⁺:YAG crystal of 68% initial transmission, 18 ns pulsewidth has been achieved with an average power of 2 W at a repetition rate of 16 kHz.     

Continuous-wave Ho:GdVO4 laser pumped by Tm-doped fiber laser with a fiber Bragg grating at room temperature

We reported the Ho:GdVO₄ laser pumped by Tm-doped laser with a fiber Bragg grating. 2.03 W continuous-wave Ho:GdVO₄ laser output power is obtained under 10.5 W incident pump power, with the optical-to-optical conversion efficiency and slope efficiency of 19.3% and 32.3%, respectively, at 7 °C. We can see that, the lower the temperature is, the better the laser output character is. The beam quality factor is M² ∼ 1.29 measured by the traveling knife-edge method.     

Diode-pumped passively Q-switched Nd:LuVO4 laser at 916 nm

We demonstrate a passively Q-switched Nd:LuVO₄ laser at 916 nm by using a Nd, Cr:YAG crystal as the saturable absorber. As we know, it is the first time to realize the laser with a simple linear resonator. When the incident pump power increased from 14.6 W to 23.7 W, the pulse width of the Q-switched laser decreased from 24 ns to 21 ns. The pulse width was insensitive to the incident pump power in the experiment. The average output power of 288 mW with repetition rate of 39 kHz was obtained at an incident pump power of 22.5 W, with the optical-to-optical efficiency and slope efficiency 1.3% and 3.6%, respectively.     

Continuous-wave broadly tunable Cr:ZnSe laser pumped by a thulium fiber laser

We describe a compact, broadly tunable, continuous-wave (cw) Cr²⁺:ZnSe laser pumped by a thulium fiber laser at 1800 nm. In the experiments, a polycrystalline ZnSe sample with a chromium concentration of 9.5 × 10¹⁸ cm⁻³ was used. Free-running laser output was around 2500 nm. Output couplers with transmissions of 3%, 6%, and 15% were used to characterize the power performance of the laser. Best power performance was obtained with a 15% transmitting output coupler. In this case, as high as 640 mW of output power was obtained with 2.5 W of pump power at a wavelength of 2480 nm. The stimulated emission cross-section values determined from laser threshold data and emission measurements were in good agreement. Finally, broad, continuous tuning of the laser was demonstrated between 2240 and 2900 nm by using an intracavity Brewster cut MgF₂ prism and a single set of optics.     

Self-Q-switched and mode-locked Nd,Cr:YAG laser with 6.52-W average output power

Simultaneous self-Q-switched and mode-locked have been demonstrated in a diode-pumped Nd,Cr:YAG laser. For the first time as we know, almost 100% modulation depth has been achieved at an intracavity intensity of 5.6 × 10⁵ W/cm². The maximum average output power of 6.52 W corresponding to a slope efficiency of 30% is obtained at 1064 nm. The laser produces high-quality pulses in a TEM₀₀-mode at the pump power of 16.5 W. The pulse duration of the mode-locked pulses is about 600 ps with 136 MHz repetition rate.     

Passively Q-switched and mode-locked diode-pumped Nd:YVO4 laser with LT-GaAs output coupler

We have demonstrated an efficient and compact passively Q-switched and mode-locked (QML) 1064 nm Nd:YVO₄ laser by using a low temperature grown GaAs (LT-GaAs) saturable absorber as well as an output coupler. Stable QML with envelope duration as short as 10 ns and Q-switched repetition rate of 36 kHz was obtained. It is the shortest envelope duration as far as we know, and it is so short that it can be used as Q-switching pulses directly. At 6.9 W of the incident pump power, average output power of 1.24 W was achieved and the corresponding peak power and energy of a single Q-switched pulse were 3.44 kW and 34.4 μJ, respectively. The mode-locked pulses inside the Q-switched pulse envelope had a repetition rate of 780 MHz.     

Diode-end-pumped passively Q-switched Nd:Y0.8Lu0.2VO4 laser with Cr:YAG crystal

A diode end-pumped passively Q-switched Nd: Y_0.8Lu_0.2VO₄ laser with a Cr⁴⁺: YAG crystal is first demonstrated in this paper. The maximum continuous wave (CW) output power of 5.59 W is obtained at the incident pump power of 13.07 W with the output transmission T = 20%, resulting in an optical-to-optical efficiency of 42.7%. For Q-switching operation, the measured pulse duration of 8.5 ns, the pulse energy of 45.24 μJ and the peak power of 5.32 kW are respectively obtained for the output transmission of 50% when the Cr⁴⁺: YAG crystal is used with an initial transmission (T₀) of 60%.     

Q-switched and mode-locked diode-pumped Nd:YAG laser with an LT-GaAs

Simultaneous Q-switching and mode-locking (QML) is accomplished in a diode-pumped Nd:YAG laser using low-temperature GaAs (LT-GaAs) as the saturable absorber, which also acts as an output coupler at the same time. The repetition rate of the Q-switched envelope increased from 25 to 40 kHz as the pump power increased from 2.2 to 6.9 W. The mode-locked pulses inside the Q-switched pulse envelope had a repetition rate of 714 MHz. A maximum average output power of 770 mW was obtained.     

Continuous-wave high-power multi-pass pumped thin-disc Nd:GdVO4 laser

A thin-disc Nd:GdVO₄ laser in multi-pass pumping scheme was developed. Continuous-wave output power of 13.9 W at 1.06 μm for an absorbed power at 808 nm of 22 W was demonstrated from a 250-μm thick, 0.5-at.% Nd:GdVO₄ in a 4-pass pumping; the slope efficiency in absorbed power was 0.65, or 0.47 in input power. Output performances were also investigated under diode laser pumping at 879 nm, directly into the emitting ⁴F_3/2 level: maximum power of 3.6 W was obtained at 6.2 W of absorbed power with 0.69 slope efficiency. Compared with pumping at 808 nm, into the highly absorbing ⁴F_5/2 level, improvements of laser parameter in absorbed power (increase of slope efficiency, decrease of threshold) were obtained, showing the advantages of the pumping into the emitting level. However, the laser performances expressed vs. the incident power were modest owing to the low absorption efficiency at 879 nm. Thus, increased number of passes of the medium would be necessary in order to match the performances in input power obtained under 808-nm pumping.     

Compact low threshold Cr:YAG passively Q-switched intracavity optical parametric oscillator

We report a compact KTP-based intracavity optical parametric oscillator (IOPO) driven by a diode-end-pumped passively Q-switched Nd:YVO₄/Cr:YAG laser. For the first time, we take the thermal lens effect of the Cr:YAG into consideration and discuss its impact on the signal output. Diode pump threshold as low as 0.52 W has been achieved, which is the lowest result reported to date. At the incident diode pump power of 4 W, we obtained the maximum signal average and peak power of 358 mW and 12.5 kW, respectively, corresponding to a diode-to-signal conversion efficiency of 9%. Moreover, cavity-dumping characteristic and pulse transforming process from 1064 to 1573 nm are qualitatively analyzed.     

Self-Q-switched and mode-locked 946 nm Cr,Nd:YAG laser

A simultaneous self-Q-switched and mode-locked diode-pumped 946 nm laser by using a Cr,Nd:YAG crystal as gain medium as well as saturable absorber is demonstrated for the first time as we know. The maximum average output power of 751 mW with a slope efficiency of 18.38% is obtained at an intra-cavity average peak power intensity of 4.83 × 10⁶ W/cm². Under this circumstance, the repetition rate of Q-switched envelopes is 9.63 kHz and the pulse width is about 460 ns. Almost 100% mode-locked modulation depth is obtained at all time in the experiment process whether the incident pump power is low or high. The repetition rate of mode-locked pulses within a Q-switched envelope is 135.13 MHz and the mode-locked pulse width is within 600 ps. The laser produces high-quality pulses in TEM₀₀-mode in the simultaneous self-Q-switched and mode-locked experiment.     

Thermal effects investigation and cavity design in passively mode-locked Nd:YVO4 laser with a SESAM

A diode-pumped passively mode-locked Nd:YVO₄ laser with a five-mirror folded cavity is presented by using a semiconductor saturable absorber mirror (SESAM). The temperature distribution and thermal lensing in laser medium are numerically analyzed to design a special cavity which can keep the power density on SESAM under its damage threshold. Both the Q-switched and continuous-wave mode-locked operation are experimentally realized. The maximum average output power of 8.94 W with a 9.3 ps pulse width at a repetition rate of 111 MHz is obtained under a pump power of 24 W, correspondingly the optical slope efficiency is 39.2%.     

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.     

Diode-pumped passively Q-switched Nd:LuxY1−xVO4 laser at 1.34 μm with two V:YAG saturable absorbers

Laser performance with the mixed Nd:Lu_0.15Y_0.85VO₄ crystal at 1.34 μm wavelength has been demonstrated. The continuous wave (cw) operation was carried out in a simple plano-concave resonator with an optical conversion efficiency of 23% and a slop efficiency of 25%. At a pump power of 6.78 W, the Q-switched pulses with the largest average output power of 349 mW, the shortest pulse width of 30.6 ns, the largest repetition rate of 42.5 kHz, the highest peak power of 268 W and the largest pulse energy of 8.2 μJ were obtained, corresponding to the V:YAG with initial transmission of 89%.     

Short pulse passively Q-switched Nd:GdYVO4 laser using a GaAs mirror

We report on a diode pumped passively Q-switched Nd:Gd_0.64Y_0.36VO₄ laser with a Cr⁴⁺:YAG saturable absorber. We show experimentally that by using an appropriately coated GaAs wafer as output coupler, the Q-switched pulse width can be significantly suppressed. Stable Q-switched pulse train with pulse width of 2.2 ns, peak power of 26.3 kW, repetition rate of 15.38 kHz have been obtained under an absorbed pump power of 8.54 W. The physical mechanism of pulse width narrowing by the GaAs wafer was also experimentally investigated.     

Continuous-wave operation of a room-temperature Ho:YAP laser pumped by a Tm:YAP laser

We reported the Ho:YAP laser pumped by the Tm:YAP laser. The Ho:YAP laser maximum output power was 4.91 W when the incident power was 10.1 W with the threshold of 2.63 W. The slope efficiency was 63.7%, corresponding to an optical-to-optical efficiency of 48.6%. The Ho:YAP output wavelength was centered at 2118.2 nm with bandwidth of about 1 nm. We estimate the beam quality to be M² = 1.29.     

Low-threshold diode-pumped CW passively mode-locked Nd:YVO4 laser

A low-threshold passively continuous-wave (CW) mode-locked Nd:YVO₄ solid-state laser was demonstrated by use of a semiconductor saturable absorber mirror (SESAM). The threshold for continuous-wave mode-locked is relatively low, about 2.15 W. The maximum average output power was 2.12 W and the optical to optical conversion efficiency was about 32%. The pulse width was about 15 ps with the repetition rate of 105 MHz.     

LD end pumped, actively mode locked and passively Q-switched Nd:YAP laser at 1341 nm

An end pumped Nd:YAP laser at 1341 nm is actively mode locked and passively Q-switched. Pumping was done with a pulsed high power laser diode with maximum power 425 W. V³⁺:YAG with 61% initial transmission served as saturable absorber, and an acousto-optic modulator is used for active mode locking. The output pulse train with 69 ns duration has a total energy of 3.2 mJ with ±4% shot-to-shot fluctuation. The peak output energy of a single mode locked pulse is 0.25 mJ. The pulse duration of a single mode locked pulse is less than 800 ps. The output laser beam is nearly diffraction limited with 1.6 mm diameter, and beam propagation factor M² about 1.3.