Master Oscillator And Power Amplifier Research Articles

13.5 μJ, 20 kHz Repetition Rate, Single Frequency Pr3+:YLF Master Oscillator Power Amplifier System

This article describes a master oscillator and power amplifier (MOPA) system with a single longitudinal mode (SLM) and high-repetition-frequency Pr3+:YLF active medium that was end-pumped by two 444 nm laser diodes. The Pr3+:YLF MOPA laser system produced a maximum pulse energy of 13.5 μJ with a pulse width of 130.2 ns at a pulse repetition frequency of 20 kHz, translating to a peak power of around 103.7 W. The Pr3+:YLF MOPA laser system’s output wavelength was 639.7 nm, and the line-width of its laser spectra was roughly 168 MHz. Additionally, at the highest output level, the laser beam quality did not decrease much due to amplification.

High-power DUV picosecond pulse laser with a gain-switched-LD-seeded MOPA and large CLBO crystal.

We report the generation of a 266 nm deep ultraviolet (DUV) picosecond pulse with an average output power of 14 W by the fourth-harmonic generation (FHG) from two consecutive frequency-doubling stages of a 1064 nm pulse based on a gain-switched-laser-diode (LD)-seeded hybrid fiber/solid-state master oscillator and power amplifier (MOPA) system. Through the gain-switched operation of a narrow-spectral-linewidth distributed-feedback laser diode and by using a Yb-doped fiber and a two-stage ${\rm Nd}:{{\rm YVO}_4}$Nd:YVO4 solid-state amplifier, we achieved an average power of 46.5 W near the Fourier transform limit for a 13 ps pulse with a repetition rate of 200 kHz. The narrow linewidth pulse characteristics enabled highly efficient frequency conversion, and the efficiency of conversion from 532 to 266 nm was 54%, and from 1064 to 266 nm was 31%. The beam quality factor ${M^2}$M2 of the generated DUV pulse was below 1.2. The highly efficient FHG process resulted in appeasing thermal stress caused by nonlinear absorption in the crystal, and more than 5000 h of continuous operation were achieved without any power down or beam profile degradation.

High-repetition-rate laser ultrasonic generation in carbon-fiber-reinforced plastics excited by a 3.2-3.4 μm ZGP master oscillator power amplifier system.

In this paper, we demonstrate 1-kHz-repetition-rate laser ultrasound in carbon-fiber-reinforced plastics (CFRPs). A ZGP master oscillator and power amplifier (MOPA) system was used to generate high-repetition-rate laser radiation in the spectral range 3.2-3.4μm. At the output wavelength of 3.4μm, the maximum output energy of the ZGP MOPA system is 5.62mJ with a pulse width of 24ns, corresponding to a peak power of approximately 233.9kW. The ultrasound was generated by the laser converted from 3.2 to 3.4μm in the graphite/epoxy composite. The maximum ultrasonic signal amplitude in the CFRP sample was 36.2mV in the condition of thermoelastic excitation at 3.4μm. Ablation occurred in the CFRP sample when the energy fluence was over 90 mJ/cm2. Compared in different samples, laser-ultrasound generation was influenced by the wavelength of the laser.

Modeling of scaling of a diode longitudinally pumped metastable rare gas with a master oscillator power amplifier.

There has been recent interest in diode pumped metastable rare gas lasers (DPRGLs) and their scaling to higher powers, due to the advantages of excellent beam quality and high quantum efficiency. In this paper, a cw diode pumped rare gas amplifier (DPRGA) with single-pass longitudinally pumped configuration is studied theoretically based on master oscillator and power amplifier (MOPA). A five-level kinetic model of DPRGAs is first established. Then, the influences of gain medium density, pump and seed laser intensities and gain length on DPRGA performance are simulated and analyzed. The results of numerical simulation agree well with those of Rawlins et al.'s experiment. With the best set of working parameters, the amplification factor reaches 22.18 dB, at pump intensity of 50 kW/cm2 and seed laser intensity of 100 W/cm2. Parameter optimization is helpful for design of a relatively high-power DPRGL system.

110.4 mJ, 1 kHz repetition rate, Ho:YAG master oscillator power amplifier.

We reported a high-energy, high-pulse-repetition-frequency Ho:YAG master oscillator and power amplifier (MOPA), which was resonantly dual-end pumped by Tm:YLF lasers at room temperature. At a pulse repetition frequency of 1kHz, the Ho:YAG MOPA laser system produced a maximum pulse energy of 110.4mJ with a 28ns pulse width, corresponding to a peak power of approximately 3.94MW. The output wavelength of the Ho:YAG MOPA laser system was 2090.9nm. In addition, a beam quality factor M2 of about 1.7 was achieved at maximum output level.

High-repetition-rate single-frequency Ho:YAG MOPA system.

A stable, 2.09μm single-frequency Ho:YAG master oscillator and power amplifier (MOPA) system at a pulse repetition frequency of 1.25kHz is demonstrated. The maximum output energy of the single-frequency injection-seeded laser is 13.76mJ, and the corresponding pulse width is 178.9ns. The seed laser is a continuous-wave Ho:YAG non-planar ring oscillator laser. The half-width of the pulse spectrum is measured to be 2.65MHz by using the heterodyne technique, which is about 1.06 times Fourier transform limited.

An 11.6 W output, 6 kHz linewidth, single-polarization EDFA-MOPA system with a (13)C(2)H(2) frequency stabilized fiber laser.

We demonstrate a record high CW output power of 11.6 W and an ultra-narrow linewidth of 6 kHz in an all-fiber master oscillator and power amplifier (MOPA) fiber laser system. The master oscillator is a (13)C(2)H(2) frequency-stabilized single-polarization fiber laser with a 100 mW output. The power amplifier section consists of a core-pumped polarization-maintained erbium-doped fiber pumped by a 1480 nm cascaded Raman fiber laser. A total electric-to-optical conversion efficiency with a record high value of 12% was achieved with an all-fiber configuration.

A 52-mJ Ho:YAG Master Oscillator and Power Amplifier with Kilohertz Pulse Repetition Frequency

We report on a high energy, high repetition rate Ho:YAG master oscillator and power amplifier (MOPA), resonantly dual-end-pumped by Tm:YLF lasers at room temperature. At the pulse repetition frequency of 1 kHz, we demonstrate a maximum energy of 30 mJ per pulse with a 28.2 ns pulse width in a Ho:YAG oscillator system resonantly double-end-pumped by Tm:YLF lasers. A maximum energy of 52 mJ per pulse with a 30.5 ns pulse width is achieved in the Ho:YAG amplifier, corresponding to a peak power of approximately 1.7 MW. The output wavelength is at 2090.6 nm and 2096.9 nm, and a beam quality factor of M2 ∼ 2.1 is achieved.

A 1 kHz, 30 mJ Ho:YAG master oscillator and power amplifier resonantly double-end-pumped by Tm:YLF lasers

We report on a high energy, high repetition rate acousto-optically Q-switched operation of Ho:YAG master oscillator and power amplifier (MOPA) resonantly double-end-pumped by Tm:YLF lasers at room temperature. For the system output, a maximum pulse energy of 30.2 mJ at the PRF of 1 kHz with a pulse width of 35 ns was achieved, corresponding to a peak power of approximately 857 kW. The output was dual-wavelength at 2090.5 and 2096.5 nm with beam quality factor of M2 ∼ 1.2.

Flexible CO2 laser system for fundamental research related to an extreme ultraviolet lithography source

A CO(2) laser system with flexible parameters was developed for fundamental research related to an extreme ultraviolet (EUV) lithography source. The laser is a master oscillator and power amplifier (MOPA) system, consisting of a master oscillator, an externally triggered plasma switch, a preamplifier, a main amplifier, and electronic synchronization units. The laser pulse duration can be varied easily from 10 to 110 ns, with a constant peak power for pulse durations from 25 to 110 ns. The MOPA laser system can also be operated in dual-oscillator mode to produce laser pulse with pulse duration as long as 200 ns and a train of laser pulses with flexible interval. The divergence of the laser beam is 1.3 times the diffraction limit. The laser intensity on the target surface can be up to 8x10(10) W/cm(2). Utilizing this CO(2) MOPA laser system, high conversion efficiency from laser to in-band (2% bandwidth) 13.5 nm EUV emission has been demonstrated over a wide range of laser pulse durations.

Optimization of erbium-doped fiber MOPA laser

An erbium-doped fiber laser (EDFL) constructed in a master oscillator and power amplifier (MOPA) configuration is analyzed. The pump powers for the fiber cavity laser and the booster amplifier stages are managed properly to achieve maximal pump conversion efficiency. Our design achieves a pump conversion efficiency of 91.4%, corresponding to a quantum efficiency of 96.6%, for a 1565.8 nm MOPA laser pumped by a total power of 300 mW at 1480 nm. The optimized MOPA laser shows a 25% enhancement in the pump conversion efficiency, compared to a non-MOPA fiber laser. A side lobe suppression ratio of 48 dB for the optimized MOPA laser is observed.

High SBS-threshold single-mode single-frequency monolithic pulsed fiber laser in the C-band

We report a high SBS-threshold, single-frequency, single-mode, polarization maintaining (PM) monolithic pulsed fiber laser source in master oscillator and power amplifier (MOPA) configuration that can operate over the C-band. In order to achieve a narrow transform-limited linewidth for pulses longer than 100 ns, we use a single-frequency Q-switched fiber laser seed, which itself can be seamlessly tuned up to 1.24 micros. The Q-switched pulses are amplified in the power amplifier stage of MOPA using a high SBS threshold single-mode PM large core highly Er/Yb co-doped phosphate glass fiber (LC-EYPhF). This seed and amplifier combination represents the first monolithic, all-fiber implementation of a single-frequency pulsed laser with the highest pulse energy of 54 microJ and peak power of 332 W for 153-ns pulses at 1538 nm.

Clad-pumped Er3+/Yb3+-codoped short pulse fiber laser with high average power output exceeding 2W

A clad-pumped short pulse Er3+/Yb3+-codoped fiber laser based on master oscillator and power amplifier (MOPA) structure, integrating the performances of broad-band tunable wavelength, uniform output power spectrum, high repetition rate and high average power to together, is proposed and demonstrated. Combining the cavity parameter optimization of the fiber master oscillator and power fiber amplifier with gain saturation characteristic of erbium-doped fiber, we achieved a lasing output with uniform output power and continuously tunable wavelength in the range from 1535 to 1530nm (i.e. 35nm band width). The maximum output power fluctuation is no more than 0.5 dBm, the average power is about 2 W, pulse repetition rate is greater than 10 GHz and pulse width is less than 30 ps in the whole tunable wavelength band width. Furthermore, the laser has advantages of good performance, simple all-fiber structure and convenient operation.

Design of End-Pumped Thin Rod Yb:YAG Laser Amplifiers

An end-pumped thin rod Yb:YAG laser amplifier architecture is proposed for high-power and efficient pulse amplification of quasi-four-level lasers. A thin and long laser rod with low ion concentration is used and optimum conditions of the laser crystal properties are discussed for efficient amplification of high-repetition-rate pulses. A high single-pass gain is expected and the thermal birefringence loss is significantly smaller than the single-pass gain. From these results, high optical conversion efficiency of more than 50% is expected for pulse amplification in the master-oscillator and power-amplifier (MOPA) system.

All solid-state pulsed ultraviolet laser widely tunable down to 188.5 nm

A nanosecond all solid-state laser operation in wide spectral range from infrared (960 nm) to deep ultraviolet (DUV) (188.5 nm) have been developed and investigated. Laser is based on Ti:sapphire master-oscillator and power amplifier (MOPA) configuration, and a set of BBO harmonics generators. Diffraction limited output of ≈0.1 mJ at 188.5 nm and ⩾1 mJ for wavelength ⩾193 nm in ultraviolet (UV) spectral range was obtained. Narrow laser linewidth ⩽0.03 nm for all harmonics was achieved by using intracavity holographic spectral selector. The combination of holographic selector and Fabry–Perot etalon provides to narrow laser line to 0.002 nm.

Dioder-pumped self-Q-switched Cr4+, Nd3+: YAG laser with amplifier

This paper reports results of study on self-Q-switched Cr4+, Nd3+: YAG microchip lasers at 1.064 μm using a quasi-monolithic setup. Pulses with 6 to 60 ns wide (FWHM) and TEM00 mode produced under cw pumping with repetition rates ranging from 1.5 kHz to 23 kHz. Pulsed pumping yielded output pulses with repetition rates from 1Hz to several kHz and excellent pulse stability. A pulsed pumped microchip oscillator and flash lamp pumped amplifiers were used to set up a MOPA (Master Oscillator and Power Amplifier) system generating 225 kW pulses with 8 ns width.