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Characteristics of Q-switched cladding-pumped ytterbium-doped fiber lasers with different high-energy fiber designs

Renaud, CC; Offerhaus, HL; Alvarez-Chavez, JA; Nilsson, J; Clarkson, WA; Turner, PW; Richardson, DJ; (2001) Characteristics of Q-switched cladding-pumped ytterbium-doped fiber lasers with different high-energy fiber designs. IEEE Journal of Quantum Electronics , 37 (2) 199 - 206. 10.1109/3.903069.

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Abstract

We theoretically and experimentally analyze Q-switched cladding pumped ytterbium-doped fiber lasers designed For high pulse energies. We compare the extractable energy from two high-energy fiber designs: 1) single- or few-moded low-NA large mode area (LMA) fibers and 2) large-core multimode fibers, which may incorporate a fiber taper for brightness enhancement. Our results show that the pulse energy is proportional to the effective core area and, therefore, LMA fibers and multimode fibers of comparable core size give comparable results. However, the energy storage in multimode fibers is mostly limited by strong losses due to amplified spontaneous emission (ASE) or even spurious lasing: between pulses. The ASE po power increases with the number of modes In a Fil,er, Furthermore, spurious feedback is more difficult to suppress,with a higher NA, and Rayleigh back-scattering increases with higher NA, too. These effects are smaller in low-NA LMA fibers, allowing for somewhat higher energy storage. For the I,RIA fibers, we found that facet damage was a more severe restriction than ASE losses or spurious lasing. With a modified laser cavity, we could avoid facet damage in the I,MA Fiber, and reached output pulse energies as high as 2.3 mJ, limited by ASE, Theoretical estimates suggest that output pulse energies around 10 mJ are feasible with a larger core Fiber, while maintaining a good beam quality.

Type: Article
Title: Characteristics of Q-switched cladding-pumped ytterbium-doped fiber lasers with different high-energy fiber designs
DOI: 10.1109/3.903069
Publisher version: http://dx.doi.org/10.1109/3.903069
Language: English
Additional information: © 2001 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.
Keywords: double-cladding, fiber laser, large core fiber, Q-switched laser, ytterbium, PULSE AMPLIFICATION, OPTIMIZATION, AMPLIFIERS, EMISSION
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Electronic and Electrical Eng
URI: https://discovery.ucl.ac.uk/id/eprint/19401
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