Fiber Master Oscillator Power Amplifier Research Articles

High-energy pulsed operation of a Yb fibre master oscillator power amplifier with an amplified spontaneous emission light source

We report high-energy pulsed operation of an amplified spontaneous emission (ASE) light source at 1050 nm based on a Yb-doped fiber master oscillator power amplifier (MOPA). The ASE seed beam with a tailored spectral bandwidth was temporally modulated by an acousto-optic modulator and was amplified in three Yb fiber amplifier stages. The MOPA yielded 320.7 µJ and 415.0 µJ of the pulsed outputs at a 100 kHz repetition rate for the ASE seeds with 1 nm and 2 nm bandwidths, respectively. Investigation of stimulated Brillouin scattering (SBS) in Yb fibers showed that ASE light pulses could offer a higher pulse energy than laser pulses due to the higher SBS threshold. We will discuss the prospects of further power scaling in a fiber ASE light source with a broad bandwidth by overcoming the SBS limitation.

Dual-wavelength-pumped Tm3+-doped ZBLAN fiber MOPA at 813 nm

We report a dual-wavelength-pumped (1220 nm + 1050 nm) Tm3+-doped ZBLAN fiber master oscillator power amplifier (MOPA) system at 813 nm for the lattice laser of the Sr optical lattice clock (OLC). Since the photodarkening effect of the Tm3+-doped fiber is more serious in the 800 nm region, it was suppressed by applying real-time photobleaching with a 532 nm laser for obtaining stable output. We also investigated the dependence of conversion efficiency on the launched pump power ratio (P1220 nm/P1220+1050 nm) and found that the maximum conversion efficiency of 50% was obtained from the pump power ratio of 41%. By installing real-time photobleaching and dual-wavelength pumping, our MOPA system generated the maximum output power of 1.95 W with slope efficiency of 48%, which is the highest output power at around 810 nm from fiber laser sources, to the best of our knowledge.

High-Peak-Power Tunable Source at 550 nm From a Frequency-Doubled Yb-Doped Fiber MOPA

A high-peak-power tunable green source operating in the range of 544–552 nm is demonstrated through frequency doubling a diode-seeded, nanosecond, polarization-maintaining, Yb-doped fiber master oscillator power amplifier system. Type I second-harmonic generation was implemented in a lithium triborate crystal via noncritical phase matching by temperature tuning. Narrow-bandwidth green light of average output power of up to 9 W, with a pulse duration of 1.8 ns and a peak power of 25 kW, was obtained at a repetition rate of 200 kHz. The pump-to-green conversion efficiency reached 30%. This linearly polarized, narrow bandwidth, tunable source has great potential for applications, such as material processing, sensing, and medical research.

Patterning of aluminum metallized pet film using high repetition rate fiber laser

The authors propose a method for rapid laser isolation of a 12 μm-thick aluminum (Al) metallized polyethylene terephthalate (PET) film. The laser patterning system employed a cost-effective, nanosecond-pulsed master-oscillator power amplifier fiber laser. A dynamic focusing configuration was adopted as a replacement of conventional telecentric lens setup for beam focusing and beam delivery. The ablation process caused thermal removal of Al, and the effects of processing parameters on ablated channels' width, depth, edge quality, and electrical isolation were investigated. It was found that a higher deposited laser energy caused the kerf width to increase. The chance of electrical isolation also increased with it at a cost of risk to damage surrounding electrode and substrate layers. Based on the findings, a processing recipe was established. Channels with a minimum width of 42 μm could be produced at a scan speed of 900 mm/s without visible collateral damage inflicted to the PET film. Finally, the process was modeled using the finite element method and validated against the experimental data.

Generation of noise-like pulses with a 920 fs pedestal in a nonlinear Yb-doped fiber amplifier.

We demonstrate the compression of noise-like pulses in an Yb-doped fiber master-oscillator power-amplifier (MOPA). The seed source of the MOPA is an NPR mode locked fiber laser delivering 5.94-ps dissipative soliton pulses with a repetition rate of 37.48 MHz. After amplification in the Yb-doped fiber amplifier, stable noise-like pulses with maximum power of 5 W are obtained. Subsequently a grating pair is used to tailor the spectrum and compensate the dispersion of the amplified noise-like pulses. The pedestal of de-convolution autocorrelation trace is compressed from 6.5 ps to 920 fs. To the best of our knowledge, this is the first time that the pedestal of a noise-like pulse is compressed to femtosecond region.

106 W, picosecond Yb-doped fiber MOPA system with a radially polarized output beam

We report the generation of high average output power, high peak power, and high pulse energy radially polarized picosecond pulses from a compact gain-switched laser-diode-seeded Yb-doped fiber master oscillator power amplifier (MOPA) system. A q-plate was employed as a mode converter prior to the final power amplifier to efficiently convert the linearly polarized Gaussian-shaped beam into a donut-shaped radially polarized beam. The desired vector beam was efficiently amplified yielding ∼110 ps pulses with a maximum output pulse energy of ∼30.7 μJ and a peak power of ∼280 kW at a repetition rate of 1.367MHz. The average power was scaled up to 106W by increasing the repetition rate to 5.468MHz.

Corrections to “An Adjustable EIT-Based FBG in Yb:Silica Master-Oscillator Fiber Power-Amplifier System” [Apr 18 Art. no. 6800409

In [1] , the biography for Maryam Eilchi should have read as follows: Maryam Eilchi received the Ph.D. degree in laser physics from the Amirkabir University of Technology, Tehran, Iran. In 2015, she joined the Nuclear Science And Technology Research Institute, as an Assistant Professor. She has been working on fiber lasers and amplifiers, laser fusion, and laser accelerators. She has authored and co-authored several papers in refereed journals and international conferences, and holds two chapters in the book FiberLaser (InTechOpen). Her current research focuses on quantum optics and quantum information. She is currently a Juror of Elsevier journals and the Journal of Optoelectronical Nanostructures .

Widely Tunable, Narrow-Linewidth, High-Peak-Power, Picosecond Midinfrared Optical Parametric Amplifier

We report a widely tunable, narrow-linewidth, midinfrared cascaded optical parametric generator–optical parametric amplifier (OPG–OPA) based on orientation-patterned GaAs pumped by a 46-ps, 1-MHz, 1952-nm diode-seeded thulium(Tm) doped fiber master oscillator power amplifier (MOPA). The Tm-doped-fiber MOPA beam was split by a polarizing beam splitter into two arms to pump the OPG and OPA stages, respectively. The generated signal from the OPG was spectrally filtered by a diffraction grating combined with an adjustable aperture to act as the tunable seed light for the OPA. Widely tunable output in the range of 2552–2960 nm (signal) and 5733–8305 nm (idler) was obtained from the OPA with narrow linewidths of 1.4 cm–1 (signal, 2942 nm) and 9 cm –1 (idler, 5800 nm), respectively. The maximum pulse energy of 0.40 μ J (signal, 2942 nm) and 0.16 μ J (idler, 5800 nm) was obtained at an overall conversion efficiency of 22.4% for the OPA stage. The pulse duration of the generated signal was 36 ps and assuming the generated idler had the same pulse duration the corresponding maximum peak powers were calculated to be 11.1 kW (signal) and 4.5 kW (idler), respectively.

Watt-level green random laser at 532 nm by SHG of a Yb-doped fiber laser.

We have developed a watt-level random laser at 532nm. The laser is based on a 1064nm random distributed ytterbium (Yb) gain-assisted fiber laser seed with a 0.35nm linewidth and 900mW polarized output power. A study for the optimal length of the random distributed mirror was carried out. A Yb-doped fiber master oscillator power amplifier architecture is used to amplify the random seeder laser without additional spectral broadening up to 20W. By using a periodically poled lithium niobate crystal in a single-pass configuration, we generate in excess of 1W random laser at 532nm by second-harmonic generation (SHG) with an efficiency of 9%. The green random laser exhibits an instability <1%, an optical signal-to-noise ratio >70 dB, a 0.1nm linewidth, and excellent beam quality.

Yb-doped large mode area fiber for beam quality improvement using local adiabatic tapers with reduced dopant diffusion.

A newly designed all-solid step-index Yb-doped aluminosilicate large mode area fiber for achieving high peak power at near diffraction limited beam quality with local adiabatic tapering is presented. The 45µm diameter fiber core and pump cladding consist of active/passively doped aluminosilicate glass produced by powder sinter technology (REPUSIL). A deliberate combination of innovative cladding and core materials was aspired to achieve low processing temperature reducing dopant diffusion during fiber fabrication, tapering and splicing. By developing a short adiabatic taper, robust seed coupling is achieved by using this Yb-doped LMA fiber as final stage of a nanosecond fiber Master Oscillator Power Amplifier (MOPA) system while maintaining near diffraction limited beam quality by preferential excitation of the fundamental mode. After application of a fiber-based endcap, the peak power could be scaled up to 375 kW with high beam quality and a measured M2 value of 1.3~1.7.

Compact millijoule diode-seeded two-stage fiber master oscillator power amplifier using a multipass and forward pumping scheme.

The multipass scheme for a diode-seeded fiber master oscillator power amplifier with a nanojoule-to-millijoule output energy level at a repetition rate of <100 kHz is numerically analyzed for comparison to an experimental benchmark. For a 6/125 single-mode preamplifier with a small input energy (<1 nJ), there is a significant improvement in the output energy from 0.7% to 80% and 95% of the maximum extractable energy using the double-pass and four-pass schemes, respectively. For a 30/250 large-mode-area power amplifier using the double-pass and forward pumping scheme, the required input energy is decreased from 100μJ to 18μJ for millijoule energy extraction with accompanying Stokes waves of less than 10% of the total energy. The system based on the full master oscillator power amplifier configuration with an output energy exceeding millijoule level can be optimally simplified to two stages for commercialization.

Arbitrary temporal shape pulsed fiber laser based on SPGD algorithm

A novel adaptive pulse shaping method for a pulsed master oscillator power amplifier fiber laser to deliver an arbitrary pulse shape is demonstrated. Numerical simulation has been performed to validate the feasibility of the scheme and provide meaningful guidance for the design of the algorithm control parameters. In the proof-of-concept experiment, information on the temporal property of the laser is exchanged and evaluated through a local area network, and the laser adjusted the parameters of the seed laser according to the monitored output of the system automatically. Various pulse shapes, including a rectangular shape, ‘M’ shape, and elliptical shape are achieved through experimental iterations.

High-power nanosecond pulse generation from an integrated Tm-Ho fiber MOPA over 2.1 μm.

In this paper, we report on high-power stable nanosecond pulse generation at ~2.1 μm from an integrated Tm-Ho all-fiber master oscillator power amplifier (MOPA) system. A total output power of 128.5 W is generated from the Tm-Ho hybrid MOPA, with an average power of 99.1 W from Ho emission at 2116 nm; the corresponding pulse repetition frequency and pulse width are 161 kHz and 322 ns, respectively, leading to a peak power of 1.91 kW. The Tm-Ho integrated master oscillator is designed to operate at 1980 and 2116 nm, where the former wavelength serves as the pump of the Ho-doped fiber. Stable laser pulses are generated from both the Tm and Ho oscillators owing to mutual modulation of emission from the two lasers. The prospects for further scaling in output power at ~2.1 μm using Tm-Ho integrated MOPA system are discussed.

295-kW peak power picosecond pulses from a thulium-doped-fiber MOPA and the generation of watt-level >2.5-octave supercontinuum extending up to 5 μm.

We report a gain-switched diode-seeded thulium doped fiber master oscillator power amplifier (MOPA) producing up to 295-kW picosecond pulses (35 ps) at a repetition rate of 1 MHz with a good beam quality (M2 ~1.3). A narrow-band, grating-based filter was incorporated within the amplifier chain to restrict the accumulation of nonlinear spectral broadening and counter-pumping of a short length of large-mode-area (LMA) fiber was used in the final stage amplifier to further reduce nonlinear effects. Finally, we generated watt-level >2.5-octave supercontinuum spanning from 750 nm to 5000 nm by using the MOPA output to pump an indium fluoride fiber.

5.6 kW peak power, nanosecond pulses at 274 nm from a frequency quadrupled Yb-doped fiber MOPA.

A 2 W deep-ultraviolet (DUV) source at 274 nm with 5.6 kW peak power is demonstrated by frequency quadrupling a diode-seeded, polarization-maintaining (PM), Yb-doped fiber master oscillator power amplifier (MOPA) system delivering 1.8 ns pulses at a repetition rate of 200 kHz. The second harmonic generation (SHG) and the fourth harmonic generation (FHG) are achieved by using Lithium Triborate (LBO) crystal and β-BaB2O4 (BBO) crystal in sequence, with an IR-to-green and green-to-UV conversion efficiency of up to 65% and 26%, respectively. This is the first kW peak power pulsed UV system reported at 274 nm which has great potential for machining insulators, 2D materials, isotopic separation of Calcium-48, and fluorescence analysis of biological molecules.

Highly efficient nanosecond 560 nm source by SHG of a combined Yb-Raman fiber amplifier.

We demonstrate a nanosecond 560 nm pulse source based on frequency-doubling the output of a combined Yb-Raman fiber amplifier, achieving a pulse energy of 2.0 µJ with a conversion efficiency of 32% from the 976 nm pump light. By introducing a continuous-wave 1120 nm signal before the cladding pumped amplifier of a pulsed Yb:fiber master oscillator power amplifier system operating at 1064 nm, efficient conversion to 1120 nm occurs within the fiber amplifier due to stimulated Raman scattering. The output of the combined Yb-Raman amplifier is frequency-doubled to 560 nm using a periodically poled lithium tantalate crystal with a conversion efficiency of 47%, resulting in an average power of 3.0 W at a repetition rate of 1.5 MHz. The 560 nm pulse duration of 1.7 ns and the near diffraction-limited beam quality (M2≤1.18) make this source ideally suited to biomedical imaging applications such as optical-resolution photoacoustic microscopy and stimulated emission depletion microscopy.

Femtosecond laser inscribed cladding waveguide lasers in Nd:LiYF4 crystals

Depressed circular cladding, buried waveguides were fabricated in Nd:LiYF4 crystals with an ultrafast Yb-doped fiber master-oscillator power amplifier laser. Waveguides were optimized by varying the laser writing conditions, such as pulse energy, focus depth, femtosecond laser polarization and scanning velocity. Under optical pump at 799 nm, cladding waveguides showed continuous-wave laser oscillation at 1047 nm. Single- and multi-transverse modes waveguide laser were realized by varying the waveguide diameter. The maximum output power in the 40 μm waveguide is ∼195 mW with a slope efficiency of 34.3%. The waveguide lasers with hexagonal and cubic cladding geometry were also realized.

25 W single-frequency, low noise fiber MOPA at 1120 nm.

This Letter reports on the development of a 25W single-frequency, all-fiber master oscillator power amplifier (MOPA) operating at 1120nm. By heating the gain fiber at 75°C, an output power of 25.3W is achieved with an optical-to-optical efficiency of 53.5%. The output shows no sign of stimulated Brillouin scattering and the signal to amplified spontaneous emission ratio is close to 40dB. A M2 value of 1.15 and a polarization extinction ratio of 17dB are measured. The relative intensity noise of the output is also characterized, reaching -155 dBc/Hz at 10MHz at the maximum output power. The study of the noise dynamics highlights, for the first time to the best of our knowledge, an unpredicted behavior due to the strong backward amplified spontaneous emission.

Watt-level single-frequency tunable neodymium MOPA fiber laser operating at 915-937 nm.

We have developed a Watt-level single-frequency tunable fiber laser in the 915-937nm spectral window. The laser is based on a neodymium-doped fiber master oscillator power amplifier architecture, with two amplification stages using a 20mW extended cavity diode laser as seed. The system output power is higher than 2W from 921 to 933nm, with a stability better than 1.4% and a low relative intensity noise.

Narrow Spectrum Kilowatt-Level MOPA Seeded By Yb-Doped Random Fiber Laser

We proposed and experimentally demonstrated an approach to achieving a narrow spectrum kilowatt-level fiber master oscillator power amplifier (MOPA). The MOPA is seeded by a narrow spectrum random laser with Yb-doped fiber gain and has the spectral broadening-free feature. The narrow spectrum property is sustained during power scaling due to the suppression of nonlinear process. The frequency and time domain of the random laser are well characterized. The proposed one-stage scheme eventually produces 1.105- and 1.073-kW output at 1064 and 1067 nm, and the 3-dB bandwidth are 0.40 and 0.47 nm, corresponding to 0.38- and 0.37-nm random laser seed, respectively. The beam quality of $\text {M}^{2}\approx 1.4$ is achieved at 1.105-kW power level, and the proposed MOPA has the potential of wavelength tunability by simply tuning the fiber Bragg grating of random laser seed.