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.     

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.     

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.     

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.     

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.     

4.44 W of CW 515 nm green light generated by intracavity frequency doubling Yb:YAG thin disk laser with LBO

We demonstrate the generation of 515 nm green laser with diode-pumped Yb:YAG thin disk by intracavity frequency doubling of type-I phase-matched LiB₃O₅(LBO) in a V-type cavity at room temperature. A continuous-wave (CW) output power of 4.44 W at 515 nm was obtained. Optical-optical efficiency of 515 nm green laser is 14.6%. The fluctuation of green laser was 1.6% at the maximum output power in 0.5 h. Thermal lensing effects in Yb:YAG thin disk are investigated too.     

Efficient passively Q-switched operation of a diode-pumped Nd:GGG laser with a Cr:YAG saturable absorber

The continuous-wave (cw) and passive Q-switching operation of a diode-end-pumped gadolinium gallium garnet doped with neodymium (Nd:GGG) laser at 1062 nm was realized. A maximum cw output power of 6.9 W was obtained. The corresponding optical conversion efficiency was 50.9%, and the slope efficiency was determined to be 51.4%. By using Cr⁴⁺:YAG crystals as saturable absorbers, Q-switching pulse with average output power of 1.28 W, pulse width of 4 ns and repetition rate of 6.2 kHz were obtained. The single-pulse energy and peak power were estimated to be 206 μJ and 51.6 kW, respectively. The conversion efficiency of the output power from cw to Q-switching operation was as high as 84.7%.     

Diode-pumped passively mode-locked Nd:GdVO4 laser at 912 nm

We have demonstrated the stable mode-locked Nd:GdVO₄ laser operating on the ⁴F_3/2-⁴I_9/2 transition at 912 nm. With a four-mirror-folded cavity and a semiconductor saturable absorber mirror for passive mode-locking, we have gained 6.5 ps laser pulses at a repetition rate of 178 MHz. The laser is diode-end-pumped, and the total output power from the out coupler is 128 mw at an incident pump power of 19.7 W.     

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: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.     

43 W picosecond laser and second-harmonic generation experiment

Combining the advantages of diode-end-pumped Nd: YVO₄ and diode-side-pumped Nd: YAG amplifiers, a high average power and high beam quality picosecond laser is designed. The system delivers a picosecond laser with average power of 43.4 W and good beam quality of M² < 1.7. By focusing the high power picosecond laser in LBO crystal, 532 nm green laser with maximal power of 20.8 W is generated and the conversion efficiency of second-harmonic generation reaches 56.4% when 17.7 W green laser obtained from the fundamental frequency laser with power of 31.4 W and beam quality of M² < 1.25.     

Investigation of Nd:YVO4/YVO4 composite crystal and its laser performance pumped by a fiber coupled diode laser

Thermal effect control is critical to scale the output power of diode end-pumping solid lasers to several watts up and beyond. Diffusion bonding crystal has been demonstrated to be an effective method to relieve the thermal lens for the end-pumping laser crystal. The temperature distribution and thermal lens in Nd:YVO₄/YVO₄ composite crystal was numerically analyzed and compared with that of Nd:YVO4 crystal in this paper. The end-pumping Nd:YVO₄/YVO₄ composite crystal laser was set up and tested with z cavity. The maximum output power of 9.87 W at 1064 nm and 6.14 W at 532 nm were obtained at the pumping power of 16.5 W. The highest optical-optical conversion efficiencies were up to 60% at 1064 nm and 40% at 532 nm, respectively.     

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.     

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.     

Passive Q-switching of short-length Tm-doped silica fiber lasers by polycrystalline Cr:ZnSe microchips

We demonstrate passive Q-switching of short-length double-clad Tm³⁺-doped silica fiber lasers near 2 μm pumped by a laser diode array (LDA) at 790 nm. Polycrystalline Cr²⁺:ZnSe microchips with thickness from 0.3 to 1 mm are adopted as the Q-switching elements. Pulse duration of 120 ns, pulse energy over 14 μJ and repetition rate of 53 kHz are obtained from a 5-cm long fiber laser. As high as 530 kHz repetition rate is achieved from a 50-cm long fiber laser at ∼10-W pump power. The performance of the Q-switched fiber lasers as a function of fiber length is also analyzed.     

High-power continuous-wave diode-end-pumped intracavity-frequency-doubled Nd:GdVO4/LBO red laser

A high-power continuous-wave (CW) diode-end-pumped intracavity-frequency-doubled red laser is reported here. The laser consists of a 0.3 at.% Nd:GdVO₄ crystal as laser gain medium, a type II non-critical phase-matched (NCPM) LBO crystal or a type I critical phase-matched (CPM) LBO crystal as frequency-doubler, and a three-mirror-folded cavity. At incident pump power of about 41 W, maximum output powers of 3.8 W and 3 W at 671 nm are obtained with corresponding optical-to-optical conversion efficiency of 9.3% and 7.5%, respectively. During half an hour, the instability of the red beam is less than 3% at output of 3 W.     

Diode-end-pumped linear-polarized single-frequency Tm:YAG laser at room temperature

By using two solid uncoated etalons, we present a diode-pumped linear-polarized single-frequency Tm:YAG laser operating at 2 μm. Placing one 0.1 mm F-P etalon at nearly Brewster angle in the cavity, the linear-polarization laser is achieved. The other 1 mm F-P etalon was turned in the range of very small angle, single-longitudinal-mode (SLM) could be obtained. The maximum output power of linear-polarized single-frequency laser of 60 mW is achieved at the wavelength of 2013 nm. The degree of the polarization is over 30 dB. Long-term frequency stability was also investigated, with the results of wavelength fluctuation about 2.55 × 10⁻¹³ m within 3 min and frequency change about 18.86 MHz, corresponding to a frequency stability of 1.27 × 10⁻⁷.     

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.     

Three-level operation of a diode-bar-pumped Yb:S-FAP laser

We present an all solid-state Yb:S-FAP laser system running on the three-level laser transition at 985 nm. The pump source was a high fill-factor laser diode bar, with the output reformatted using a two-mirror beamshaping system to produce a rectangular pump beam that focused to a square spot. A nearly on-axis multipassing system was used to obtain four pump passes through a 1.6 mm Yb:S-FAP laser crystal. Gain-switched three-level laser output was achieved with an efficiency of 4.3% with respect to incident pump power. Electro-optic Q-switching produced 0.12 mJ pulses for a pump pulse energy of 11 mJ. Intra-cavity second-harmonic generation yielded a maximum pulse energy at 492.5 nm of 12 μJ.     

Quasi-three-level Nd:YAG laser under diode pumping directly into the emitting level

We present theoretical and experimental investigations on ground-state direct pumping at 869 nm into the emitting level ⁴F_3/2 of end-pumped quasi-three-level Nd:YAG lasers operating at 946 nm. We have demonstrated, what we believe is for the first time, a Nd:YAG laser at 946 nm directly pumped by diodes and obtained 1.6 W of output power.