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

Characteristics of Q-switched cladding-pumped ytterbium-doped fiber lasers with different high-energy fiber designs
Characteristics of Q-switched cladding-pumped ytterbium-doped fiber lasers with different high-energy fiber designs
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 power increases with the number of modes in a fiber.

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 LMA 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 LMA 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
double-cladding, fiber laser, large core fiber, q-switched laser, ytterbium
0018-9197
199-206
Renaud, Cyril C.
0977146a-9cae-4401-95d5-3478a2b1f351
Offerhaus, H.L.
75130d34-dbad-4f37-bbd4-08fa7c0f9d4b
Alvarez-Chavez, J.A.
fbbf6f21-0e7a-456c-b675-540b4f0501d1
Nilsson, J.
f41d0948-4ca9-4b93-b44d-680ca0bf157b
Clarkson, W.A.
3b060f63-a303-4fa5-ad50-95f166df1ba2
Turner, P.W.
b84fbbe4-2e35-4d0d-9b84-e654be63c4b9
Richardson, D.J.
ebfe1ff9-d0c2-4e52-b7ae-c1b13bccdef3
Grudinin, A.B.
8f50b467-7d60-46db-b29d-a89b1059a1d8
Renaud, Cyril C.
0977146a-9cae-4401-95d5-3478a2b1f351
Offerhaus, H.L.
75130d34-dbad-4f37-bbd4-08fa7c0f9d4b
Alvarez-Chavez, J.A.
fbbf6f21-0e7a-456c-b675-540b4f0501d1
Nilsson, J.
f41d0948-4ca9-4b93-b44d-680ca0bf157b
Clarkson, W.A.
3b060f63-a303-4fa5-ad50-95f166df1ba2
Turner, P.W.
b84fbbe4-2e35-4d0d-9b84-e654be63c4b9
Richardson, D.J.
ebfe1ff9-d0c2-4e52-b7ae-c1b13bccdef3
Grudinin, A.B.
8f50b467-7d60-46db-b29d-a89b1059a1d8

Renaud, Cyril C., Offerhaus, H.L., Alvarez-Chavez, J.A., Nilsson, J., Clarkson, W.A., Turner, P.W., Richardson, D.J. and Grudinin, A.B. (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. (doi:10.1109/3.903069).

Record type: Article

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 power increases with the number of modes in a fiber.

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 LMA 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 LMA 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

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Published date: 2001
Keywords: double-cladding, fiber laser, large core fiber, q-switched laser, ytterbium

Identifiers

Local EPrints ID: 13729
URI: https://eprints.soton.ac.uk/id/eprint/13729
ISSN: 0018-9197
PURE UUID: ddbe8775-fe7d-4b8b-aacc-c92e73fb2365
ORCID for J. Nilsson: ORCID iD orcid.org/0000-0003-1691-7959
ORCID for D.J. Richardson: ORCID iD orcid.org/0000-0002-7751-1058

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Date deposited: 22 Dec 2004
Last modified: 03 Dec 2019 02:05

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Contributors

Author: Cyril C. Renaud
Author: H.L. Offerhaus
Author: J.A. Alvarez-Chavez
Author: J. Nilsson ORCID iD
Author: W.A. Clarkson
Author: P.W. Turner
Author: D.J. Richardson ORCID iD
Author: A.B. Grudinin

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