Master Oscillator Power Amplifier Laser Research Articles

Method to improve beam quality by compensating spherical aberrations in master oscillator power amplifier laser systems.

A method is presented for beam quality improvement, in master oscillator power amplifier laser systems. Intensive study was first carried out with the beam wavefront evolution in a laser resonator. When the laser beam propagates inside the resonator, the spherical aberration coefficient of the beam wavefront can change sign, i.e., the negative spherical aberration coefficient can turn to positive, and vice versa. This process also occurs when the beam propagates outside the resonator in a free space. The laser beam, from an oscillator with negative spherical aberration, was found to be well-compensated by the positive spherical aberration of a strongly pumped laser rod in a laser amplifier. The laser beam quality M2 factor has been significantly improved, from 2.2 to 1.4, while the output power has been scaled from 31W up to 60W.

200 ps pulse generation at 1180 nm with a SrWO4 Raman crystal pumped by a sub-nanosecond MOPA laser system

We are reporting Raman conversion experiments with a SrWO4 crystal in a single-pass traveling-wave setup. As a pump source we employed a master oscillator power amplifier (MOPA) laser system at 1064 nm, delivering 200 µJ, 500 ps long pulses at a 9 kHz maximum repetition rate with limited diffraction beam quality. At 2 kHz we obtained up to 45 µJ pulse energy and 200 ps pulse duration at 1180 nm, with a conversion efficiency of 22%. Up to the maximum incident average pump power of 1.35 W no serious beam quality degradation was observed, and we measured a factor M2 ⩽ 1.5 for the Raman shifted beam.

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 Brightness 556 nm Laser by Frequency Doubling of a 1112 nm Nd:YAG Laser

We demonstrate an efficient high power and high brightness yellow-green 556-nm laser generated from second harmonic generation (SHG) of a master oscillator power amplifier (MOPA) laser system at 1112 nm. The oscillator was a pulsed laser diode (LD) pumped and Q-switched Nd:YAG laser at 1112 nm operated at TEM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">00</sub> mode with an average output power of 35 W, providing 200-μs long macropulses and constituting 700-ns micropulses. The seed laser was amplified by two LD side-pumped Nd:YAG amplifiers and the MOPA system delivered a maximum output power of 78 W. Using a type-I phase-matching lithium triborate nonlinear crystal, the SHG maximum output power of 48 W was obtained at 556 nm with a conversion efficiency as high as 61.5%. The beam quality factor was measured to be M <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> = 1.53 and the corresponding brightness was as high as 6.63 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">9</sup> W/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ·sr.

High OSNR watt-level single-frequency one-stage PM-MOPA fiber laser at 1083 nm

A 1.03 W optical signal-to-noise ratio (OSNR) of > 70 dB single-frequency polarization-maintained master-oscillator power amplifier (PM-MOPA) laser at 1083 nm was demonstrated. The seed laser of this laser system was a distributed Bragg reflector short cavity Yb-doped phosphate fiber oscillator. A one-stage core-pumped amplification configuration was employed, in which the typical gain is 9.7 dB and the optical-to-optical conversion efficiency is 68.7%. The estimated laser linewidth is less than 3.5 kHz, the measured polarization-extinction ratio is greater than 25 dB, and the obtained relative intensity noise of fiber laser for frequencies of over 2 MHz is less than -130 dB/Hz.

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.

Low repetition rate, hybrid fiber/solid-state, 1064 nm picosecond master oscillator power amplifier laser system

We report on an investigation of a passively mode-locked picosecond ytterbium-doped fiber laser with a repetition rate close to 1 MHz. The mode-locking operation was induced by a butt-coupled semiconductor saturable absorber mirror (SESAM) and stabilized in the normal dispersion regime by means of spectral filtering of a narrow bandwidth (0.1 nm) fiber Bragg grating (FBG). A pulse duration of about 50 ps with maximum output power of 20 mW at 1064 nm were achieved after amplification in the double-pass fiber preamplifier. This compact and reliable all-fiber laser operating at 1064 nm is intended to seed bulk amplifiers in a hybrid fiber/solid-state configuration. Employing a two-stage Nd:YVO4 amplifier, we obtained 10 W average output power, which preserved both the quasi-diffraction limited beam quality and spectral purity of the seeder. Second harmonic generation (SHG) with 50% conversion efficiency was demonstrated in type-II potassium titanyl phosphate (KTP) and type-I angle phase matched lithium triborate (LBO) crystal. Furthermore, a space independent numerical model was developed in order to study the dependence of intracavity pulse energy on the main design parameters of the master oscillator (cavity length, FBG bandwidth, SESAM modulation depth) within the stability range (single pulse per round trip in CW mode-locking operation) of the fiber laser master oscillator.

109 W kHz-linewidth one-stage all-fiber linearly-polarized MOPA laser at 1560 nm

An all-fiber 10.9 W single-frequency one-stage linearly-polarized master-oscillator power amplifier (MOPA) laser at 1560 nm has been demonstrated. The laser linewidth is less than 3.5 kHz and the polarization-extinction ratio (PER) is greater than 24 dB. The measured signal-to-noise ratio (SNR) is higher than 70 dB and the optical-to-optical conversion efficiency is 29.5%. No obvious stimulated Brillouin scattering and the devastating effects of unwanted coupling light were observed.

Narrowband, mid-infrared, seeded optical parametric generator based on non-critical CdSiP2 pumped by 120-ps, single longitudinal mode 1,064 nm pulses

In this work, we present low-threshold, efficient optical parametric generation in CdSiP2 pumping at 1,064 nm with 120-ps-long, single longitudinal and transverse mode pulses at 230-kHz repetition rate provided by a microchip passively Q-switched master-oscillator power amplifier laser system. Seeding at the signal wavelength with a laser diode, we generated bandwidth-limited idler pulses at 6,100 nm.

145-watt high beam quality bidirectional voltage-supplied Q-switched Nd∶YAG master oscillator power amplifier laser

We present a high compact structure laser diode (LD) side-pumped all-solid-state Q-switched master oscillator power amplifier (MOPA) laser system with high beam quality. Bidirectional voltage-supplied Q-switched and MOPA technologies were introduced in the design. An in-center wavelength of 1064 nm with pulse width adjustability from 5 to 18 ns was obtained at the repetition rate of 500 Hz. Through multistage Nd∶YAG amplifiers at the pulse width of 6 ns, the oscillator was scaled up to 145 W and the corresponding peak power reached 48.3 MW with single pulse energy fluctuation less than 0.45% in 1 h operation.

Single-frequency linearly-polarized 1083 nm all fiber nanosecond laser

Single-frequency linearly-polarized 1083 nm all fiber nanosecond master-oscillator power amplifier laser system is demonstrated. A ring laser, whose key components are one saturable absorber and two polarization controllers, delivers a single-frequency continuous wave laser. Using an electro-optic modulator as the modulator, the pulse laser seed is obtained by modulating the CW laser. By amplifying the pulse seed to the average power of 61.6 W in three stages, a single-frequency linearly-polarized laser with pulse duration of 16 ns, repetition rate of 10 MHz and pulse energy of 6.16 μJ is obtained. No nonlinear effect is observed in our experiment. Higher output power can be obtained by increasing LDs of the main amplifier.

High-energy Ho:LLF MOPA laser system using a top-hat pump profile for the amplifier stage

Numerical simulations show the advantage of using a top-hat intensity profile pumping the amplifier stage in an Ho:LuLiF4 (Ho:LLF) master oscillator power amplifier (MOPA) configuration over a Gaussian pump profile: higher pulse energies could be generated simultaneously with reduced peak fluence in Q-switched operation. In the experimental implementation, the top-hat beam was realized with a coherent beam transformation of the non-absorbed pump beam transmitted by the oscillator to pump the amplifier stage. The Ho:LLF MOPA produced 103.6 mJ at a repetition rate of 100 Hz with a pulse duration of 30 ns at a wavelength of 2053 nm, which corresponds to an optical-to-optical efficiency of 12.9 %. The beam quality was nearly diffraction limited (M 2 = 1.03).

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.

90.4-W all-fiber single-frequency polarization-maintained 1 083-nm MOPA laser employing ring-cavity single-frequency seed oscillator

A high-power all-fiber single-frequency polarization-maintained (PM) laser operating at 1 083 nm is demonstrated using a master oscillator power amplifier (MOPA) structure. The seed source of this MOPA laser system is an in-house-built ring-cavity fiber oscillator. Four-stage amplification configuration is employed, in which the maximal output power of the main amplifier is 90.4 W, corresponding to a conversion efficiency of 72.5%. The polarization extinction ratio of the output light is 13 dB. The amplified spontaneous emission is suppressed by a factor of over 25 dB, and no stimulated Brillouin scattering effect is observed when a large-mode-area and high absorption coefficient PM gain fiber is employed.

96.2 W all-fiberized nanosecond single-frequency fiber MOPA

We report experimental results on a 96.2 W all-fiberized nanosecond single-frequency masteroscillator power amplifier (MOPA) laser working at 1064 nm. An external modulation fiber laser with average power of 0.5 mW and line width of 20 kHz is used as the seed source. Amplifying the seed laser in four stages, a single-frequency laser with pulse duration of 10 ns and peak power of 816.7 W is obtained. The average output power is up to 96.2 W. Further power-scaling of this MOPA structure can be realized since our experiment is only pump-power limited.

Quantum cascade laser master-oscillator power-amplifier with 15 W output power at 300 K

We report quantum cascade laser (QCL) master-oscillator power-amplifiers (MOPAs) at 300 K reaching output power of 1.5 W for tapered devices and 0.9 W for untapered devices. The devices display single-longitudinal-mode emission at λ = 7.26 µm and single-transverse-mode emission at TM(00). The maximum amplification factor is 12 dB for the tapered devices.

High-power 266 nm ultraviolet generation in yttrium aluminum borate

A yttrium aluminum borate [YAl(3)(BO(3))(4)] (YAB) crystal with UV cutoff wavelength of 165 nm is used as the nonlinear optical crystal for fourth harmonic generation. The fundamental frequency laser at 1064 nm from an Nd:YVO(4) master oscillator power amplifier laser was frequency doubled to 532 nm. Using the type I phase-matching YAB crystal, a 5.05 W average power 266 nm UV laser was obtained at the pulse repetition frequency of 65 kHz, corresponding to the conversion efficiency of 12.3% from 532 to 266 nm. The experimental results show great potential for the application of using YAB as a nonlinear optical crystal to get high-power fourth harmonic generation.

High-Efficiency Supercontinuum Generation at 12.8 W in an All-Fiber Device

We report 12.8 W supercontinuum generation with a high optical-to-optical conversion efficiency of up to 85% in an all-fiber device. This is achieved by using an all-fiber picosecond master oscillator power amplifier laser, which has an output pigtail double clad fiber, to pump a 3-m photonic crystal fiber with the core at one end enlarged by adiabatically collapsing two inner layers of air holes while keeping other holes open. Our experimental results show that the short-wavelength generation is due to dispersive wave trapping by redshifted solitons.

Micro-integrated 1 Watt semiconductor laser system with a linewidth of 36 kHz

We demonstrate a compact, narrow-linewidth, high-power, micro-integrated semiconductor-based master oscillator power amplifier laser module which is implemented on a footprint of 50 x 10 mm(2). A micro-isolator between the oscillator and the amplifier suppresses optical feedback. The oscillator is a distributed Bragg reflector laser optimized for narrow-linewidth operation and the amplifier consists of a ridge waveguide entry and a tapered amplifier section. The module features stable single-mode operation with a FWHM linewidth of only 100 kHz and an intrinsic linewidth as small as 3.6 kHz for an output power beyond 1 W.

主振荡功率放大激光器增益导引效应的数值模拟及分析

主振荡功率放大激光器增益导引效应的数值模拟及分析