YAG Master Oscillator Power Amplifier Research Articles

Multi-mode stable, high peak power Nd:YAG laser device for laser cleaning

High average power and peak power solid-state lasers are of great interest in the field of laser cleaning. In this research, a high peak power laser with over 400 W average power using a multi-mode stable resonator in a diode-pumped Nd:YAG master oscillator power amplifier has been demonstrated. A maximum peak power over 1.08 MW was achieved at a repetition frequency of 5 kHz. Delivery fiber with a 400 µm core diameter was utilized for flexible laser transmission. A prototype of the laser cleaning system was developed and inspiring application effects for paint and mold cleaning were achieved.

1064 nm laser pumped optical parametric oscillator based on BaGa4Se7 crystal at 1 kHz repetition rate

In this work, a tunable mid-infrared optical parametric oscillator based on type I phase-matching BaGa4Se7 was demonstrated. Using a Nd:YAG master oscillator power amplifier system as pump source, we firstly achieve the 1064 nm pumped BGSe-OPO at 1 kHz repetition rate. With pump double-pass single resonant oscillator configuration, the maximum output power at 4.18 μm was 483 mW and the corresponding conversion efficiency is 8.78 %. Both temperature and angle tuning of BGSe-OPO were studied and widely tunable output in the range of 3.36–5.16 μm was obtained. The average power fluctuation measured within 30 min was 0.98 % root mean square. This study has unveiled the great potential of BGSe crystal in highly stable, widely tunable, high repetition rate mid-infrared pulse generation.

1.36 J nanosecond laser at 1 kHz repetition based on a slab amplifier chain.

A high beam quality diode-pumped Nd:YAG master oscillator power-amplifier (MOPA) laser with three end-pumped slab amplifiers is developed. The Q-swtiched side-pumped rod oscillator presented a pulse energy 3.1mJ with beam quality factors of M x2=1.17 and M y2=1.15 at a repetition of 1kHz. The MOPA system delivered a pulse energy of 1.36J with a pulse width of 48.2ns and an extraction efficiency of 44.8%. The beam quality factors of M x2=1.72 and M y2=3.85 are measured without any phase-conjugators or adaptive optics.

Thermal-birefringence-induced depolarization in a 450 W Ho:YAG MOPA system.

We demonstrated an efficient, high-power Ho:YAG master-oscillator power amplifier (MOPA) system and investigated its thermal-birefringence-induced depolarization. The maximum output power was 450 W with a depolarized power of 32.1 W and depolarization of 0.071 via three power amplifiers. To our knowledge, this is the highest average power generated from a Ho:YAG MOPA system. In theory, a simplified model was built to calculate the depolarization in the amplifier, and the theoretical results agreed with the actual value well. Moreover, the overall optical-to-optical efficiency of the MOPA system was near 60%, and the beam quality M2 factors of s-polarized laser were measured to be ∼ 1.8 at 400 W. In pulse operation, the per pulse energy was ∼ 11 mJ at the pulse repetition frequency of 40 kHz with the corresponding peak power of 220 kW.

High-stability, high-pulse-energy MOPA laser system based on composite Nd:YAG crystal with multiple doping concentrations

In this paper, a high-stability, high-pulse-energy laser at a repetition rate of 2 kHz was presented from an electro-optically Q-switched Nd:YAG master oscillator power amplifier (MOPA) system. A multi-segment composite Nd:YAG crystal was utilized as the gain medium of the electro-optically Q-switched laser, yielding a pulse energy of 8.6 mJ and a pulse width of 7.8 ns at 2 kHz. By using two laser diode (LD) end-pumped Nd:YAG amplifiers, the single pulse energy was amplified to 28.6 mJ, corresponding to a peak power of 3.7 MW. By frequency doubling with a LiB3O5 (LBO), 13.2 mJ and 6.4 ns laser pulses were achieved at 532 nm. With the temperature varying from −40℃ to 55℃, the coefficient of variation (CV) of the pulse energy was 2.6%. Besides, the laser system also presented high stability under the typical vibration condition of the airborne platform. This MOPA laser system is a promising laser source for airborne remote sensing.

High stability 500 Hz MOPA system for planar laser-induced fluorescence

A high pulse energy laser diode-pumped Nd:YAG master oscillator power amplifier (MOPA) laser is demonstrated. The maximum energy of 68 mJ, 9.6 ns, 1064 nm laser at a pulse repetition frequency of 500 Hz is achieved by utilizing the amplifier composed of three LD side-pumped Nd:YAG modules. Moreover, the maximum laser energy of 35.6 mJ is obtained at 532 nm by employing a KTP crystal as a frequency doubler. When ambient temperature ranges from 5 °C to 45 °C, the master oscillator has a pulse energy jitter of <5%. During the shake-environment test, the maximum-pulse-energy jitter of the MOPA laser is less than 2%. The developed MOPA laser has been used in a laser-induced fluorescence system and the variation of the flow field is obtained at a repetition rate of 500 Hz.

A High-Energy, Narrow-Pulse-Width, Long-Wave Infrared Laser Based on ZGP Crystal

In this paper, we present a high-energy, narrow pulse-width, long-wave infrared laser based on a ZnGeP2 (ZGP) optical parametric oscillator (OPO). The pump source is a 2.1 μm three -stage Ho:YAG master oscillator power-amplifier (MOPA). At a repetition frequency of 1 kHz, the Ho:YAG MOPA system outputs the maximal average power of 52.1 W, which corresponds to the shortest pulse width of 14.40 ns. By using the Ho:YAG MOPA system as the pump source, the maximal average output powers of 3.15 W at 8.2 μm and 11.4 W at 2.8 μm were achieved in a ZGP OPO. The peak wavelength and linewidth (FWHM) of the long-wave infrared laser were 8156 nm and 270 nm, respectively. At the maximal output level, the pulse width and beam quality factor M2 were measured to be 8.10 ns and 6.2, respectively.

5.4 W, 9.4 ns Pulse Width, Long-Wave Infrared ZGP OPO Pumped by Ho:YAG MOPA System

We demonstrated a narrow pulse-width long-wave infrared ZnGeP <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> (ZGP) optical parametric oscillator (OPO) pumped by a 2.1 μm Ho:YAG master oscillator power-amplifier (MOPA). By short-cavity structure, a minimum pulse width of ~12 ns was achieved at 1kHz, 2kHz and 3kHz in Ho:YAG oscillator. By employing a three-stage amplifier, a maximum average output power of 73.1 W with pulse width of ~17 ns at the pulse repetition frequency of 3 kHz was obtained. Then a ZGP OPO pumped by the Ho:YAG MOPA was demonstrated. The maximum average output powers of 5.48 W at 8.2 μm and 22.4 W at 2.8 μm were obtained, corresponding to the pulse width of <; 10 ns.

161 W middle infrared ZnGeP2 MOPA system pumped by 300 W-class Ho:YAG MOPA system.

We demonstrated a high-power Q-switched two-stage Ho:YAG master-oscillator power-amplifier (MOPA) system dual-end pumped by Tm:YLF lasers. A new method was introduced by rotating and swapping spatial axial directions of pump beams to improve the beam quality of the Ho:YAG oscillator and first-stage amplifier. Two parallel second-stage Ho:YAG amplifiers were employed to output high power. A total maximum average output power of 332 W at 2091 nm with pulse repetition frequency of 20 kHz was achieved. Then a ZnGeP2 MOPA system was demonstrated using the Ho:YAG MOPA as the pump source. A maximum average output power of 161 W at 3-5 µm was obtained with 290 W incident Ho pump power, corresponding to beam quality factors M2 of 3.42 and 3.83 for horizontal and vertical directions, respectively.

231 W dual-end-pumped Ho:YAG MOPA system and its application to a mid-infrared ZGP OPO.

A high-efficiency and high-brightness Ho:YAG master-oscillator power-amplifier (MOPA) system dual-end pumped by Tm:YLF lasers was demonstrated. The maximum output power of 231W at a wavelength of 2090.7nm was achieved with pulse repetition frequency of 10kHz and pulse width of 22.9ns, corresponding to pulse energy of 23.1mJ and peak power of ∼1 MW. The extraction efficiency of the amplifier system was more than 60%. The beam quality factor M2 was measured to be ∼1.05. Using the Ho:YAG MOPA system as the pump source, the ZnGeP2 optical parametric oscillator delivered an output power of 110W, corresponding to slope efficiency of 62%.

High-Power Narrow-Linewidth Q-Switched TEM00 Mode 355-nm Laser

We report on a high pulse energy, narrow-linewidth, Q-switched ultraviolet (UV) laser at 355 nm from the third harmonic generation (THG) of a 1064-nm Nd:YAG master oscillator power amplifier (MOPA) system. An output of 37 W at 355 nm was obtained with a pulse duration of 32 ns and a linewidth of ∼2.5 pm. The beam-quality factor was measured to be $M^{2}$ = 1.24. This is, to the best of our knowledge, the highest average power for a Q-switched narrow-linewidth TEM00 UV laser at 355 nm. Meanwhile, a multimode laser rate equations model was used for theoretical analysis on the linewidth and pulse duration of the fundamental laser oscillator for the first time, and the calculated results agree well with the experimental data.

High brightness laser based on Yb:YAG MOPA chain and adaptive optics system at room temperature.

We demonstrate a master oscillator power amplifier (MOPA) architecture based on Yb:YAG amplifiers and adaptive optics (AO) systems with a high power and high beam quality laser output. With two conduction cooled, dual-end-pumped Yb:YAG zigzag-slab amplifiers at room temperature, the fiber laser of 300 W was scaled to 11.9 kW. Moreover, AO system positioned downstream was utilized to correct wavefront of amplified laser. The beam quality β at maximum output power was 2.8 times diffraction limited with closed-loop AO system.

Laser-diode-pumped Nd:YVO4/Nd:YAG MOPA burst-mode laser

We report a high-repetition-rate, high-peak-power laser diode (LD) pumped burst-mode 1064 nm laser from a Nd:YVO4/Nd:YAG master oscillator power amplifier. 10–100 kHz pulse burst in a duration up to 2 ms is achieved in LD end-pumped Nd:YVO4 acousto-optically Q-switched laser. After amplification with LD side-pumped Nd:YAG rod amplifiers, the single pulse energy reaches 73 mJ in 10 kHz pulse burst laser with a peak power of 7.8 MW.

High-power QCW microsecond-pulse solid-state sodium beacon laser with spiking suppression and D2b re-pumping.

A 65 W quasi-continuous-wave microsecond-pulse solid-state sodium beacon laser tuned to the sodium D2a line has been developed with a linewidth of 0.3 GHz, beam quality of M2=1.38, and pulse width of 120 μs at a repetition rate of 500 Hz by sum-frequency mixing 1319 and 1064 nm diode-pumped Nd:YAG master-oscillator power-amplifier systems. The laser wavelength stability is less than ±0.15 GHz through feedback controlling. The laser spiking due to relaxation oscillations is suppressed by inserting frequency doublers in both 1319 and 1064 nm oscillators. Sodium D2b re-pumping is accomplished by tuning the frequency of the electro-optic modulator with the right D2a-D2b offset. A bright sodium laser guide star with a photon return of 1820 photons/cm2/s was achieved with the laser system when a 32 W circular polarized beam was projected to the sky during our field test at the Xinglong Observatory.

33 W quasi-continuous-wave narrow-band sodium D2a laser by sum-frequency generation in LBO

We demonstrate an all-solid quasi-continuous-wave (QCW) narrow-band source tunable to sodium D2a line at 589.159 nm. The source is based on sum-frequency mixing between lasers at 1064 nm and 1319 nm in a LBO crystal. The 1064 nm and 1319 nm lasers are produced from two diode side-pumped Nd:YAG master oscillator power amplifier (MOPA) laser systems, respectively. A 33 W output of 589 nm laser is obtained with beam quality factor M2 = 1.25, frequency stability better than ±0.2 GHz and linewidth less than 0.44 GHz. A prototype 589 nm laser system is assembled, and a sodium laser guided star has been successfully observed in the field test.

High power diode-side-pumped 1 112-nm Nd:YAG laser based on master-oscillator power-amplifier system

We demonstrate a high power high beam quality diode-pumped 1 112-nm Nd:YAG master-oscillator poweramplifier (MOPA) laser system. To increase the extraction efficiency and output power, a four-pass amplifier scheme is employed. Finally, the injected laser output power is amplified from 26 to 64 W with beam quality factor M2=2.85. Furthermore, a theoretical model that takes the temporal overlap inversion number dynamics into account is employed to analyze the performance of the MOPA laser system, and a good agreement with the experimental data is obtained.

High-efficiency nanosecond optical parametric oscillator with the stable ring configuration

High stability nanosecond OPO operation at 1.57 μm was realized based on the type II non-critically phase-matched (NCPM) KTP crystal by utilizing a single frequency Nd:YAG master oscillator power amplifier (MOPA) laser as pump source. Energy conversion efficiency of 18.1% was demonstrated with single-pass ring cavity which was approximately two times more than that of critical ring cavity. The highest slope efficiency of 37.76% and maximum signal pulse energy of 3.1 mJ were attained with the output reflectivity of R = 50% at the pulse repetition frequency of 100 Hz. Experimental results reveal that the nanosecond OPO with ring stable configuration is a promising design to meet the need of IPDA’s transmitter.

Operation of a Raman laser in bulk silicon

A Raman laser based on a bulk silicon single crystal with 1.127 μm emission wavelength is demonstrated. The Si crystal with 30 mm length was placed into an external cavity and pumped by a Q-switched Nd:YAG master oscillator power amplifier system. Strong defocusing of the pump and Raman laser beam by free carriers was compensated by an intracavity lens. Raman laser operation with a pulse duration of 2.5 ns was identified by a Raman laser threshold significantly lower than the single-pass stimulated Raman-scattering threshold. Linear absorption losses of the 1.06415 μm pump radiation are strongly reduced by cooling the Si crystal to a temperature of 10 K.

A 7.5 W quasi-continuous-wave sodium D2 laser generated from single-pass sum-frequency generation in LBO crystal

We report a high-power, narrow linewidth and tunable quasi-continuous-wave (QCW) yellow laser system at 589.159 nm. The system is of a design employing single-pass sum-frequency generation (SFG) in a LBO crystal by mixing the 1064 nm with 1319 nm lines from a two diode-side-pumped Nd:YAG master oscillator-power amplifier (MOPA) laser system. With the pump power of 35 W at 1064 nm and 25 W at 1319 nm, a 7.5 W QCW output of the SFG yellow laser at 589.159 nm, which is the vacuum wavelength of a general sodium D2 line, is obtained with a linewidth less than 0.7 GHz and a beam-quality factor M 2=1.2. The wavelength of the laser can be precisely step-tuned from 589.148 to 589.167 nm with an increment of 0.13 pm by means of a temperature-controlled etalon.

QCW diode-pumped 654 W AO Q-switched Nd:YAG rod oscillator-amplifier laser

A diode laser-pumped acoustic-optic Q-switched Nd:YAG master-oscillator power amplifier laser is presented. The laser is quasi continuously pumped at 1.1 kHz with a pulse width of 172 μs, and the ultrasonic frequency of the AO Q-switcher is set at a higher value (53 kHz). The master oscillator is designed as a thermally near-unstable-resonator, which presents an average output power of 48 W with a beam quality value of M 2 = 1.41 and a Q-switching pulse duration of 121 ns. The maximum average power of the MOPA system is 654 W, and the beam quality is M 2 = 6.