1,720,969 research outputs found
Multi-wavelength pumping of high power fibre Raman lasers
No full textFibre Raman lasers are an alternative to high power rare-earth-doped fibre lasers with benefits such as wavelength versatility and resilience to photodarkening. However, stimulated Raman scattering is a weak nonlinear process that requires high pump intensities, which are difficult to reach with high power multimode diode lasers, which are favoured for pumping. Nevertheless, research has shown that power-scaling of fibre Raman lasers pumped directly by such diode laser is possible. Whereas high-power diodelaser-pumped fibre Raman lasers have been investigated with only a single wavelength (narrow-bandwidth) pumping thus far, this study aims to further power-scale diode laserpumped fibre Raman laser by using wide-span multi-wavelength pumping. First, I examined two-wavelength (976 and 950 nm) pumped fibre Raman laser. Two high-power diode lasers are spectrally combined and launched into graded-index fibre. Although the separation between the two wavelengths was far from ideal (neither smaller than the Raman linewidth nor comparable to the Raman shift), the laser emitted 23 W at a single wavelength. This indicates that the separation among pump wavelengths is not so critical. Next, another three high power diode lasers at 969, 940, and 915 nm were spectrally added to the pump, expanding the total pump bandwidth to 683 cm-1 (915 – 976 nm). Three different fibres (silica-core step-index fibre, graded-index fibre with high germanium-doping, and step-index fibre with high germanium-doping) were tested. All three cases led to high-power single-wavelength output, reaching 32, 67, and 101 W, respectively. Also, this showed the advantages of germanium-doping. (e.g., higher Raman gain and pump launching efficiency) Lastly, numerical simulations showed that a pump bandwidth of up to ~1000 cm-1 can be used to pump a fibre Raman laser with an efficiency of more than 70%, for a clad-to-core area ratio up to ~7. Overall, the results show that multi-wavelength pumping of fibre Raman laser allow for efficient high power lasers. Thus, the basic concept of a multi-wavelength-pumped fibre Raman laser that may evolve into a new type of kW-laser is established in this thesis
Dataset for Off-peak dual-wavelength multimode diode-laser-pumped fiber Raman laser
No full textData supporting Hong, S., Feng, Y., & Nilsson, J. (2018). Off-peak dual-wavelength multimode diode-laser-pumped fiber Raman laser. IEEE Photonics Technology Letters, 1-4. DOI: 10.1109/LPT.2018.2863559</span
Wide-span multi-wavelength high-power diode-laser pumping of fiber Raman laser
No full textA multimode silica-core fiber Raman laser was pumped directly by five wavelength-combined multimode diode lasers. The pump wavelengths were spread over a bandwidth of 700 cm-1, namely, at 976, 969, 950, 940, and 915 nm. This is larger than the Raman peak shift of 490 cm-1. The output power reached 31.5 W with an overall slope efficiency of 42% at the wavelength of 1018 nm when pumped with the maximum launched power of 175 W. According to simulations, the fiber was under-length and the output power could double in a longer fiber. Our results suggest that pumping with spectrally combined diode lasers is a promising approach to high-power fiber Raman lasers, even when the pump wavelengths are not optimized.</p
Data for: Multi-Wavelength Diode-Pumping of Fiber Raman Laser
No full textThe data for the figures in the conference paper:
Hong, S., Feng, Y., & Nilsson, J. (2018). Multi-wavelength diode-pumping of fiber Raman laser. In Conference on Lasers and Electro-Optics: Science and Innovations 2018 Optical Society of America. DOI: 10.1364/CLEO_SI.2018.SM1K.6
A fiber Raman laser pumped by two wavelength-combined multimode diode lasers at 950 nm and 976 nm generates up to 23 W of output power at a single wavelength (1020 nm) with 51% slope efficiency.</span
Off-peak dual-wavelength multimode diode-laser-pumped fiber Raman laser
No full textWe demonstrate a fiber Raman laser directly pumped by two spectrally combined multimode diode lasers at ~950 nm and ~976 nm. The emission wavelength becomes 1020 nm, which corresponds to the 1st Stokes of 976 nm. The pump separation of 270 cm-1 is both much smaller than the Raman peak shift of 440 cm-1 and much larger than the Raman linewidth of around 100 cm-1, which is unfavorable for efficient Raman conversion. Nevertheless, the addition of the pump at 950 nm triples the output power compared to pumping only at 976 nm. We reach 23 W of output power with slope efficiency of 51% and beam quality M2 of 5.2 in a germanosilicate graded-index fiber.</p
Fiber Raman laser pumped by five wavelength-combined multimode diode lasers from 915 to 976 nm
No full textA fiber Raman laser pumped by five multimode diode lasers at 976, 969, 950, 940, and 915 nm generates 31.5 W of output power at a single wavelength of 1018 nm with 42% slope-efficiency
Multi-wavelength diode-pumping of fiber Raman laser
No full textA fiber Raman laser pumped by two wavelength-combined multimode diode lasers at 950 nm and 976 nm generates up to 23 W of output power at a single wavelength (1020 nm) with 51% slope efficiency
Simulations of multiwavelength cladding pumping of high-power fiber Raman amplifiers
No full textWe numerically simulate and optimize a high-power fiber Raman amplifier cladding pumped by spectrally combined diode lasers at wavelengths from ~0.9 to ~1µm in the continuous-wave regime. This amplified a signal at the first-Stokes wavelength of 1024 nm. We found that it was possible to add pumps over an increasingly wide wavelength span up to ~90 nm, while still maintaining an incremental conversion efficiency higher than 60%, even though the Raman linewidth is only ~15 nm. We investigated the dependence on the power of individual diode lasers and on the wavelength spacing and found that the total conversion efficiency reaches ~70 % with realistic pump sources based on state-of-the-art diode lasers. We believe this study shows the potential for high-power fiber Raman lasers pumped by spectrally combined multiwavelength diode and fiber laser sources.See also Erratum, link below
Dataset for Fiber Raman Laser Cladding Pumped by Pulsed Multimode Disk Laser at 1030 nm
No full textDataset for an article published at a conference proceedings, Conference on Lasers and Electro-Optics OSA Technical Digest (online) (Optica Publishing Group, 2018), paper JTh2A.109, https://doi.org/10.1364/CLEO_AT.2018.JTh2A.109
accepted and published by CLEO: Science and Innovations 2018, San Jose, California United States, 13–18 May 2018, ISBN: 978-1-943580-42-2, From the session: Poster Session III (JTh2A)
A spatially gain-tailored fiber Raman laser with Ge-doped core and P-doped inner cladding generates 46 W of instantaneous power at 1084 nm with 64% slope efficiency when cladding-pumped by a 1030-nm quasi-cw multimode disk laser.
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Multimode-pumped Raman amplification of a higher order mode in a large mode area fiber
No full textWe report the first demonstration of Raman amplification in a fiber of a single Bessel-like higher order mode using a multimode pump source. We amplify the LP08-mode with a 559-µm2 effective mode area at a signal wavelength of 1115 nm in a pure-silica-core step-index fiber. A maximum of 18 dB average power gain is achieved in a 9-m long gain fiber, with output pulse energy of 115 µJ. The Raman pump source comprises a pulsed 1060 nm ytterbium-doped fiber amplifier with V-value ~30, which is matched to the Raman gain fiber. The pump depletion as averaged over the signal pulses reaches 36.7%. The conversion of power from the multimode pump into the signal mode demonstrates the potential for efficient brightness enhancement with low amplification-induced signal mode purity degradation
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