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120-W Q-switched cladding-pumped Yb-doped fibre laser

120-W Q-switched cladding-pumped Yb-doped fibre laser
120-W Q-switched cladding-pumped Yb-doped fibre laser
The output powers of fibre lasers at 1µm continue to grow and such lasers are now beginning to compete with conventional solid state lasers (for example, Nd:YAG lasers) in many important application areas, e.g., material processing, medicine, range finding, etc. Fibre lasers benefit from a geometry that allows easy thermal management and an easy selection of a high quality output beam. So far a pulse energy of 7.7mJ and 10W average output power has been reported from a large core Yb-doped Q-switched fibre laser [1]. In fact, the maximum extractable energy is limited by the build-up of amplified spontaneous emission or spurious lasing between pulses [2], and thus, large-mode area (LMA) fibres are preferred. Besides the pulse energy, factors to be considered are the average power and the beam quality, which are especially important for applications operating at very high average power levels such as materials processing. In this paper, we investigate Q-switching of LMA cladding-pumped Yb-doped fibre laser in terms of its high-power operation. We designed and fabricated an LMA fibre with a 30µm diameter, 0.07 NA, core, and a 350µm D-shaped inner cladding with 0.49 NA. The continuous wave slope efficiency was ~84% with respect to the absorbed pump power at 975nm. The experimental setup for the Q-switched fibre laser is shown in Fig. 1. A diode-laser stack at 975nm was used as the pump source. The first-order diffracted beam from the acousto-optic modulator was fed back by a dichroic mirror that had a high reflectivity at ~1µm, the diffraction efficiency of which was ~70%. The fibre length was ~9m. The Q-switched pulse energy and the average power are shown in Fig. 2. A maximum pump power of 250W was launched into the fibre. We evaluated the maximum pulse energy to 8.4mJ at ~1.06µm, for a repetition rate of 0.5kHz, though with a large uncertainty because of the high level of amplified spontaneous emission present between pulses. The maximum average power at the repetition rate of 200kHz was 120W with 0.6mJ pulses. The pulse width was ~460nsec at a low repetition rate. These values are the highest that have ever been reported for a Q-switched fibre laser, to the best of our knowledge.
Jeong, Yoonchan
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Sahu, J.K.
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Laroche, M.
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Clarkson, W.A.
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Furusawa, K.
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Richardson, David
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Nilsson, J.
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Jeong, Yoonchan
94ab6f5b-7623-4061-8598-8de2e7aa751e
Sahu, J.K.
009f5fb3-6555-411a-9a0c-9a1b5a29ceb2
Laroche, M.
f45c57ba-ed2d-412e-9042-6204b466cd03
Clarkson, W.A.
3b060f63-a303-4fa5-ad50-95f166df1ba2
Furusawa, K.
f84c2a9c-89d8-41a1-9d7a-b196fc4ed60c
Richardson, David
ebfe1ff9-d0c2-4e52-b7ae-c1b13bccdef3
Nilsson, J.
f41d0948-4ca9-4b93-b44d-680ca0bf157b

Jeong, Yoonchan, Sahu, J.K., Laroche, M., Clarkson, W.A., Furusawa, K., Richardson, David and Nilsson, J. (2003) 120-W Q-switched cladding-pumped Yb-doped fibre laser. Conference on Lasers and Electro-Optics/Europe (CLEO/Europe-EQEC 2003). 23 - 27 Jun 2003. 1 pp .

Record type: Conference or Workshop Item (Paper)

Abstract

The output powers of fibre lasers at 1µm continue to grow and such lasers are now beginning to compete with conventional solid state lasers (for example, Nd:YAG lasers) in many important application areas, e.g., material processing, medicine, range finding, etc. Fibre lasers benefit from a geometry that allows easy thermal management and an easy selection of a high quality output beam. So far a pulse energy of 7.7mJ and 10W average output power has been reported from a large core Yb-doped Q-switched fibre laser [1]. In fact, the maximum extractable energy is limited by the build-up of amplified spontaneous emission or spurious lasing between pulses [2], and thus, large-mode area (LMA) fibres are preferred. Besides the pulse energy, factors to be considered are the average power and the beam quality, which are especially important for applications operating at very high average power levels such as materials processing. In this paper, we investigate Q-switching of LMA cladding-pumped Yb-doped fibre laser in terms of its high-power operation. We designed and fabricated an LMA fibre with a 30µm diameter, 0.07 NA, core, and a 350µm D-shaped inner cladding with 0.49 NA. The continuous wave slope efficiency was ~84% with respect to the absorbed pump power at 975nm. The experimental setup for the Q-switched fibre laser is shown in Fig. 1. A diode-laser stack at 975nm was used as the pump source. The first-order diffracted beam from the acousto-optic modulator was fed back by a dichroic mirror that had a high reflectivity at ~1µm, the diffraction efficiency of which was ~70%. The fibre length was ~9m. The Q-switched pulse energy and the average power are shown in Fig. 2. A maximum pump power of 250W was launched into the fibre. We evaluated the maximum pulse energy to 8.4mJ at ~1.06µm, for a repetition rate of 0.5kHz, though with a large uncertainty because of the high level of amplified spontaneous emission present between pulses. The maximum average power at the repetition rate of 200kHz was 120W with 0.6mJ pulses. The pulse width was ~460nsec at a low repetition rate. These values are the highest that have ever been reported for a Q-switched fibre laser, to the best of our knowledge.

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Published date: 2003
Venue - Dates: Conference on Lasers and Electro-Optics/Europe (CLEO/Europe-EQEC 2003), 2003-06-23 - 2003-06-27

Identifiers

Local EPrints ID: 41637
URI: https://eprints.soton.ac.uk/id/eprint/41637
PURE UUID: 3c92b3ec-8a87-46bf-aa80-b17ee56f7c65
ORCID for David Richardson: ORCID iD orcid.org/0000-0002-7751-1058
ORCID for J. Nilsson: ORCID iD orcid.org/0000-0003-1691-7959

Catalogue record

Date deposited: 11 Oct 2006
Last modified: 26 Nov 2019 02:05

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Contributors

Author: Yoonchan Jeong
Author: J.K. Sahu
Author: M. Laroche
Author: W.A. Clarkson
Author: K. Furusawa
Author: J. Nilsson ORCID iD

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