Master Oscillator Power Amplifier System Research Articles

Generation of 220 mJ nanosecond pulses at a 10 Hz repetition rate with excellent beam quality in a diode-pumped Yb:YAG MOPA system

A novel all-diode-pumped master oscillator power amplifier system based on Yb:YAG crystal rods has been developed. It consists of a Q-switched oscillator delivering 3 mJ, 6.4 ns pulses at a 10 Hz repetition rate and an additional four-pass amplifier, which boosts the output energy to 220 mJ, while a close to TEM(00) beam quality could be observed. Additionally a simulation of the amplification was written that allows for further scaling considerations.

High Pulse Energy, Rep. Rated Nd:glass Laser with Wavefront Correction

We report a high average power and high pulse energy diode-pumped Nd:glass master oscillator power amplifier system that is consisted of a thermally-edge-controlled zigzag slab amplifier and stimulated Brillouin scattering (SBS) mirror for use of pumping source of ultra intense laser system. This phase conjugated system produces an average power of 213 W at 10 Hz in 8.9-ns pulse (2.4 GW peak power) with an optical-to-optical conversion efficiency of 11.7 % and a near diffraction limited beam quality. To the best of our knowledge these results represent the highest average power achieved from a Nd:glass based laser amplifier system.

用于高重复频率热容主振荡功率放大器激光系统的波前检测技术

用于高重复频率热容主振荡功率放大器激光系统的波前检测技术

High Repetition and High Power Lasers for EUV Light Source

High repetition and high power laser development is one of the important subjects for the realization of a practical EUV light source for microlithography using 13.5 nm. This paper presents advances in Nd: YAG laser and CO2 laser development for EUV source application at Osaka University and EUVA, respectively. An average laser power of 5.2k W at 100k Hz repetition rate with 10 ns pulse width was achieved from a Nd: YAG laser system developed at Osaka University, while an average laser power of 13k W at 100k Hz repetition rate with 20 ns pulse width was achieved from a short pulse CO2 MOPA (Master Oscillator Power Amplifier) system developed at EUVA.

Phase conjugating mirror combining a fused silica rod and a fiber

A phase conjugating mirror combining a fused silica rod and an optical fiber is presented. This configuration combines a large diameter fused silica rod with a high laser damage threshold and an optical fiber with a low stimulated Brillouin scattering (SBS) threshold. The composed SBS generator-amplifier construction, similar to the two-cell type makes a forced SBS process, in which the Stokes beam reflected by the fiber is injected into the fused silica rod. Using this combined phase conjugating mirror in a laser-diode-pumped laser master oscillator power amplifier system, we obtained 42% SBS reflectivity at most at 100 Hz repetition rate. At the same time, the inverse beam quality parameter M(2) is reduced from 3 to 1.6, while at 400 Hz repetition rate, M(2) is reduced from 4 to 1.7.

Laser Transmitter for Undersea Communications Using Third-Harmonic Generation of Fiber-Laser System at 1.5 $\mu$m

We report a viable laser transmitter for free-space undersea communications. An all-fiber, picosecond, Watt-level master-oscillator-power-amplifier (MOPA) system at 1.5 mum based on rapid amplification of mode-locked pulses in heavily Er:Yb codoped phosphate fiber is combined with fiber pigtailed lithium niobate intensity modulator (pulse picker), to construct a fully integrated eye-safe transmitter operating at 65-Mb/s data rate, that can be used in intermediate-range (few kilometers) atmospheric communication links. For undersea use, the output of the MOPA system is frequency-tripled into the blue-green transparency window of ocean water. The wavelength conversion occurs in a simple single-pass setup utilizing a sequence of two periodically poled lithium niobate crystals, both of which are operated at room temperature. The conversion efficiency from fundamental to third harmonic reached 14% and resulted in generation of 140 mW of average power at 518 nm. The conversion efficiency can be straightforwardly increased threefold using properly antireflection-coated optics in the free-space part of the setup, and the data rate can be scaled up into the gigabit-per-second range by using a faster mode-locked oscillator in the MOPA system.

Simple scheme for ultraviolet time-pulse shaping

We present a method to generate high-energy flat-top UV laser pulses such as the ones needed to optimally drive high-brightness radio-frequency photoinjectors. In this scheme we believe to be novel, the longitudinal profile of a laser pulse from a Ti:sapphire master oscillator power amplifier system is controlled using a mechanical mask in the Fourier plane of a 4f stretcher located after the harmonic conversion crystals. Such a scheme allows us to overcome many of the difficulties faced by current state-of-the-art pulse-shaping designs. These are in fact based on various versions of preamplifier infrared shapers and hence suffer from the limitations set by the nonlinearities of chirped-pulse amplification and harmonic conversion. Beyond the clear advantages of simplicity and robustness, the proposed solution offers the possibility to deliver a pulse with very short rise and fall times and to freely change the output pulse length. We also note that, after proper calibration between spectral and temporal profiles, the shaper optical setup offers the possibility to retrieve the longitudinal profile of the laser pulse on a shot-to-shot basis.

A high power laser system at 540 nm with beam coupling by second harmonic generation

We present a novel coupling scheme of two independent amplified beam lines in a Nd:YAP based master oscillator power amplifier (MOPA) system. Second harmonic generation (SHG) with type II phase matching offers the possibility of coupling two perpendicularly polarized beams, which are delivered from a MOPA system with two parallel amplifier chains. To preserve the excellent oscillator beam quality after amplification, the amplifiers are driven in double pass and optical fibres as phase conjugate mirrors (PCM) are used after the first pass. With this method, a single beam with an average power of 124W is generated in the green spectral range. The laser system operates at an average repetition rate of 2.8kHz and delivers pulses with a width of 160ns.

High-power ps InGaAs diode laser MOPA system for efficient frequency doubling in periodically poled KTP

This paper reports on a mode-locked InGaAs master oscillator power amplifier (MOPA) system that generates at 920 nm 14-ps-long pulses with a repetition rate of 4.3 GHz and an average power of 2.7 W. Single-pass frequency doubling in a periodically poled KTP crystal provides 550 mW of blue 460-nm radiation. The power of the blue output, which corresponds to a conversion efficiency of more than 20%, was optimized by a detailed investigation of the influence of various system parameters like injection current and repetition rate on pulse power, pulse duration, and spectral shape of the infrared laser pulses.

Tapered-fiber phase conjugator with high stability and high reflectivity used for master-oscillator power amplifier systems

Tapered fiber phase-conjugating mirrors (PCMs) have been experimentally investigated in a master-oscillator power amplifier system. The dependence of PCM properties such as threshold and reflectivity on the geometry of the fiber is discussed. The beam quality factor M2 of the output beam was 1.2, and the peak power reached 1.1 MW. In operation with 100-Hz repetition rates, the fluctuation of the output energy was 8%. A depolarization ratio of 3% and phase conjugation fidelity above 90% were also demonstrated.

Widely and Rapidly Tunable Semiconductor Master-Oscillator Fiber Amplifier Around 1080 nm

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> We describe the wide and rapid wavelength tuning of a continuous-wave master-oscillator power-amplifier system consisting of a semiconductor-amplifier-based oscillator and an ytterbium (Yb)-doped fiber amplifier. The oscillator utilizes an acoustooptic tunable filter and an intracavity etalon to achieve wavelength tuning of 36 nm in 5 ms. The 50-mW output from the master oscillator was amplified to over 9 W in an Yb-doped fiber amplifier. </para>

Spectral shaping of a 10W diode laser-Yb-fiber amplifier system

We describe a continuous-wave master-oscillator power-amplifier system based on a distributed Bragg reflection diode laser and an Yb doped fiber amplifier. The observed optical spectrum of the amplified seed source can be tailored to arbitrary shapes and widths between 30MHz and greater than 1GHz by controlling the radio frequency modulation wave form of the injection current.

High-beam-quality, 5.1J, 108Hz diode-pumped Nd:YAG rod oscillator–amplifier laser system

A high efficiency, high beam quality diode-pumped Nd:YAG master oscillator power-amplifier (MOPA) laser with six amplifier stages is demonstrated. The oscillator with two-rod birefringence compensation was designed as a thermally determined near hemispherical resonator, which presents a pulse energy of 223 mJ with a beam quality value of M2 = 1.29 at a repetition rate of 108 Hz. The MOPA system delivers a pulse energy of 5.1 J with a pulse width of 230 μs, a M2 factor of 3.6 and an optical-to-optical efficiency of 38.5%. To the best of our knowledge, this is the highest pulse energy for a diode-pumped Nd:YAG rod laser operation with a high beam quality and a pulse width of hundreds of microseconds at a repetition rate of over 100 Hz.

Zigzag slabs for solid-state laser amplifiers: batch fabrication and parasitic oscillation suppression

We have developed a 100 W class Nd:YAG master oscillator power amplifier system based in part on an end-pumped zigzag slab power amplifier. This amplifier incorporates parasitic oscillation suppression by using roughened edges and achieves a small-signal gain coefficient (g(0)l) of 8.06. We describe a novel technique for suppression of parasitic oscillations using claddings on slab edges that significantly increases g(0)l to 11.63 and increases the single-pass extracted power in a power amplifier by 50%. Commercial use of these zigzag slab amplifiers has been limited by the time and cost of production. We describe a new batch fabrication technique that improves the quality and significantly reduces the cost of zigzag slabs.

High average power, high repetition rate, picosecond pulsed fiber master oscillator power amplifier source seeded by a gain-switched laser diode at 1060 nm

We demonstrate a pulsed ytterbium-doped fiber master-oscillator power amplifier source at 1060 nm producing over 300 W of average power in 20-ps pulses at 1-GHz repetition rate. The pulses generated by a gain-switched diode were compressed by a chirped fiber Bragg grating and amplified without any distortion with excellent spectral quality. This fiber master oscillator power amplifier system offers versatility and potential for further power scaling.

EUV radiation characteristics of a CO2 laser produced Xe plasma

A CO2 laser-driven Xe liquid jet plasma has been studied with respect to its usability as a EUV lithography light source. A short-pulse TEA-CO2 master oscillator power amplifier system (MOPA) and a pre-pulse Nd:YAG laser were used for the plasma generation. The dependence of EUV plasma parameters, e.g., conversion efficiency, plasma image, in-band and out-of-band spectra, on the delay time between the pre-pulse and the main pulse laser was investigated. A maximum conversion efficiency of 0.6% was obtained at a delay time of about 200 ns. In addition, characteristics of fast ions were measured by the time-of-flight method. The peak energy of the fast ion energy distribution decreased significantly at delay times longer than 200 ns. This result is very promising with respect to a collector mirror lifetime extension by magnetic field mitigation.

Developments of a fibre-MOPA system for the light source of the gravitational wave antenna

We have developed a fibre-MOPA (master oscillator power amplifier) system as the light source of the future gravitational wave detectors. The output power from a 500 mW NPRO emitting 1064 nm was amplified by an Yb-doped double-clad fibre amplifier, and the maximum output power and the optical–optical conversion efficiency were 12 W and 89%, respectively. The diffraction-limited beam was obtained from the multi-mode fibre amplifier by bending the fibre. The frequency noise and intensity noise of the fibre-MOPA were evaluated and suppressed.

7.4 W continuous-wave output power of master oscillator power amplifier system at 1083 nm

A 1083 nm hybrid master oscillator power amplifier system consisting of a DBR laser and a tapered amplifier has been realised. A maximum output power of 7.4 W in single-longitudinal mode operation with a narrow spectral linewidth and a sidemode suppression ratio better than 40 dB is presented.

Power scaling of a pico-second Nd:YVO4master-oscillator power amplifier with a phase-conjugate mirror

We investigated design issues for the power scaling of a pico-second Nd:YVO(4) master-oscillator power amplifier system with a photorefractive phase-conjugate mirror by using standard beam propagation analysis. We also demonstrated a 25 W diffraction-limited pico-second output. A corresponding extraction efficiency of 31 % was achieved.

Suppression of stimulated Raman scattering in a high power Yb-doped fiber amplifier using a W-type core with fundamental mode cut-off

We demonstrate the suppression of stimulated Raman scattering in a high power, single-mode Yb-doped fiber amplifier using a W-type core structure. Raman-scattered light is not guided by the core. The amplifier consists of a master oscillator power amplifier (MOPA) system, seeded with 103 ps pulses at 32 MHz repetition rate in the final amplification stage. An average output power of 53 W, which corresponds to 13 kW of peak power, was achieved in the 23 m long W-type double-clad fiber without any significant loss of power due to transfer from the signal wavelength at 1060 nm to the Raman Stokes wavelength at 1114 nm and amplified spontaneous emission from Yb-ions at longer wavelengths (~1070 nm). The power conversion efficiency at 1060 nm was 80% with respect to the absorbed pump power.