Spectrally beam combined fiber lasers for high power, efficiency, and brightness

Honea, Eric C.; Afzal, Robert S.; Savage-Leuchs, Matthias; Gitkind, Neil; Humphreys, Richard; Henrie, Jason; Brar, K.; Jander, Don

doi:10.1117/12.2021808

Cited by 28 publications

(10 citation statements)

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“…Along those lines, narrowlinewidth, kW class Yb-doped fiber amplifiers have been recently demonstrated through external phase modulation [3]. Although the effective linewidth of the laser would no longer be single-frequency, beam combining of high-power fiber amplifiers modulated at the GHz level has been demonstrated for both spectral and coherent beam combining (CBC) architectures [4][5][6]; further driving interest in kW class narrow-linewidth fiber amplifiers.…”

Section: Introductionmentioning

confidence: 99%

Pseudo-random binary sequence phase modulation for narrow linewidth, kilowatt, monolithic fiber amplifiers

et al. 2014

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We report on pseudo random binary sequence (PRBS) phase modulation for narrow-linewidth, kilowatt-class, monolithic (all-fiber) amplifiers. Stimulated Brillouin scattering (SBS) threshold enhancement factors for different patterns of PRBS modulated fiber amplifiers were experimentally analyzed and agreed well with the theoretical predictions. We also examined seeding of the SBS process by phase modulated signals when the effective linewidth is on the same order as the Brillouin shift frequency. Here ~30% variations in SBS power thresholds were observed from small tunings of the modulation frequency. In addition, a 3 GHz PRBS modulated, 1.17 kW fiber amplifier was demonstrated. Near diffraction-limited beam quality was achieved (M2 = 1.2) with an optical pump efficiency of 83%. Overall, the improved SBS suppression and narrow linewidth achieved through PRBS modulation can have a significant impact on the beam combining of kilowatt class fiber lasers.

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Section: Introductionmentioning

confidence: 99%

Pseudo-random binary sequence phase modulation for narrow linewidth, kilowatt, monolithic fiber amplifiers

et al. 2014

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“…In the case of (incoherent) spectral beam combining of multiple amplifiers with a single grating [25], CSA will give rise to rapid beam steering. A dual-grating technique could convert the steering into a beam displacement that could be less problematic for directed energy applications [26].…”

Section: Discussionmentioning

confidence: 99%

Chirped Laser Seeding for SBS Suppression in a 100-W Pulsed Erbium Fiber Amplifier

White

Engin

Akbulut

et al. 2015

IEEE J. Quantum Electron.

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A pulsed Er/Yb fiber amplifier is seeded with a frequency-chirped diode laser for the purpose of suppressing stimulated Brillouin scattering (SBS), as an alternative to the conventional broadband seed. SBS in the final stage of the amplifier limits the output power. A chirp of 5 · 10 15 Hz/s is seen to increase the SBS threshold by nine times, compared with the case with no chirp. The final stage of the amplifier is modeled with a system of equations that are solved for the laser field, Stokes field, acoustic field, pump power, amplified spontaneous emission power, Yb inversion, and Er inversion, as a function of z and t. The experimental and theoretical results are in good agreement. The SBS threshold scales linearly with chirp, when the effective seed linewidth (the product of chirp and fiber transit time) is much greater than the Brillouin linewidth.

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“…E/O efficiencies >39% have already been demonstrated by multi-kW spectrally beam combined fiber-coupled diode lasers (Honea et al, 2013). Focused development under the DARPA SHEDs program has also lead to extremely high power conversion efficiency in the 9xx-nm wavelength band, leading to diode bars with efficiency in excess of 74% and a clear route to efficiencies superior to 85% at room temperature (Crump et al, 2007).…”

Section: Laser Ablationmentioning

confidence: 99%

Statistical multi-criteria evaluation of non-nuclear asteroid deflection methods

Thiry

Vasile

2017

Acta Astronautica

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This version is available at https://strathprints.strath.ac.uk/61691/ Strathprints is designed to allow users to access the research output of the University of Strathclyde. Unless otherwise explicitly stated on the manuscript, Copyright © and Moral Rights for the papers on this site are retained by the individual authors and/or other copyright owners. Please check the manuscript for details of any other licences that may have been applied. You may not engage in further distribution of the material for any profitmaking activities or any commercial gain. You may freely distribute both the url (https://strathprints.strath.ac.uk/) and the content of this paper for research or private study, educational, or not-for-profit purposes without prior permission or charge.Any correspondence concerning this service should be sent to the AbstractIn this paper we assess and compare the effectiveness of four classes of nonnuclear asteroid deflection methods applied to a wide range of virtual collision scenarios. We consider the kinetic impactor, laser ablation, the ion beaming technique and two variants of the gravity tractor. A simple but realistic model of each deflection method was integrated within a systematic approach to size the spacecraft and predict the achievable deflection for a given mission and a given maximum mass at launch. A sample of 100 synthetic asteroids was then created from the current distribution of NEAs and global optimisation methods were used to identify the optimal solution in each case according to two criteria: the minimum duration between the departure date and the time of virtual impact required to deflect the NEA by more than two Earth radii and the maximum miss-distance achieved within a total duration of 10 years. Our results provide an interesting insight into the range of applicability of individual deflection methods and argue the need to develop multiple methods in parallel for a global mitigation of all possible threats.

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Spectrally beam combined fiber lasers for high power, efficiency, and brightness

Cited by 28 publications

References 0 publications

Pseudo-random binary sequence phase modulation for narrow linewidth, kilowatt, monolithic fiber amplifiers

Pseudo-random binary sequence phase modulation for narrow linewidth, kilowatt, monolithic fiber amplifiers

Chirped Laser Seeding for SBS Suppression in a 100-W Pulsed Erbium Fiber Amplifier

Statistical multi-criteria evaluation of non-nuclear asteroid deflection methods

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