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Bendable large-mode-area fiber with a non-circular core

Bendable large-mode-area fiber with a non-circular core
Bendable large-mode-area fiber with a non-circular core
We investigate mode-area-scaling and bending performances of a Yb-doped large-mode-area fiber with an elongated non-circular core. Such fiber can be bent in the plane of its short axis to suppress bending effects, such as mode area reduction and mode profile distortion. Meanwhile, the other orthogonal axis can be stretched for mode area scaling. Calculations show that for fibers with the same mode area, the higher the aspect ratio between the long axis and short axis, the less sensitive the fiber will be to bending effects. However, mode area scaling is limited by the increased beat length (BL) between the fundamental mode (FM) and the second-order mode, leading to mode degeneracy at higher aspect ratios. Within the 100 mm BL, the FM area is scalable to 3000 μm2 in a bent fiber. To facilitate FM operation, we study mode-selective gain through confined doping. Thanks to the small bending distortions, the confined-doping approach works well in the bent large-mode-area fiber. In addition, the advantage of tandem pumping is also discussed in terms of preferential modal gain. A noncircular core fiber with a 41 μm short axis and 120 μm long axis was fabricated in-house. We evaluated the fiber in a linear laser cavity pumped by a 975 nm laser diode. The maximum output power obtained was 191 W, with slope efficiency of approximately 67% with respect to launched pump power. The output signal has good beam qualities with M2 of ∼1.5 and ∼3.1, respectively, along the short and long axis.
See also:  Publishers' note- Applied Optics 57(29) 8518  (2018)https://doi.org/10.1364/AO.57.008518
1559-128X
6388-6395
Ji, Junhua
6aa66acf-2138-4e0a-8a5e-63b199cb81b2
Lin, Huaiqin
0e8f318a-0864-4c8f-803b-9fd9f13009f5
Sidharthan, Raghuraman
ea6ed907-3e88-499c-8273-e2a45d53c619
Ho, Daryl
7723e9b0-1180-4485-b537-19aa60418787
Zhou, Yanyan
22220329-f67f-4457-bde5-6491b6055c86
Nilsson, Johan
f41d0948-4ca9-4b93-b44d-680ca0bf157b
Yoo, Seongwoo
f56cdc58-c6c4-4536-b15a-2bacf26ca7f8
Ji, Junhua
6aa66acf-2138-4e0a-8a5e-63b199cb81b2
Lin, Huaiqin
0e8f318a-0864-4c8f-803b-9fd9f13009f5
Sidharthan, Raghuraman
ea6ed907-3e88-499c-8273-e2a45d53c619
Ho, Daryl
7723e9b0-1180-4485-b537-19aa60418787
Zhou, Yanyan
22220329-f67f-4457-bde5-6491b6055c86
Nilsson, Johan
f41d0948-4ca9-4b93-b44d-680ca0bf157b
Yoo, Seongwoo
f56cdc58-c6c4-4536-b15a-2bacf26ca7f8

Ji, Junhua, Lin, Huaiqin, Sidharthan, Raghuraman, Ho, Daryl, Zhou, Yanyan, Nilsson, Johan and Yoo, Seongwoo (2018) Bendable large-mode-area fiber with a non-circular core. Applied Optics, 57 (22), 6388-6395. (doi:10.1364/AO.57.006388).

Record type: Article

Abstract

We investigate mode-area-scaling and bending performances of a Yb-doped large-mode-area fiber with an elongated non-circular core. Such fiber can be bent in the plane of its short axis to suppress bending effects, such as mode area reduction and mode profile distortion. Meanwhile, the other orthogonal axis can be stretched for mode area scaling. Calculations show that for fibers with the same mode area, the higher the aspect ratio between the long axis and short axis, the less sensitive the fiber will be to bending effects. However, mode area scaling is limited by the increased beat length (BL) between the fundamental mode (FM) and the second-order mode, leading to mode degeneracy at higher aspect ratios. Within the 100 mm BL, the FM area is scalable to 3000 μm2 in a bent fiber. To facilitate FM operation, we study mode-selective gain through confined doping. Thanks to the small bending distortions, the confined-doping approach works well in the bent large-mode-area fiber. In addition, the advantage of tandem pumping is also discussed in terms of preferential modal gain. A noncircular core fiber with a 41 μm short axis and 120 μm long axis was fabricated in-house. We evaluated the fiber in a linear laser cavity pumped by a 975 nm laser diode. The maximum output power obtained was 191 W, with slope efficiency of approximately 67% with respect to launched pump power. The output signal has good beam qualities with M2 of ∼1.5 and ∼3.1, respectively, along the short and long axis.
See also:  Publishers' note- Applied Optics 57(29) 8518  (2018)https://doi.org/10.1364/AO.57.008518

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Accepted/In Press date: 27 June 2018
e-pub ahead of print date: 28 June 2018
Published date: 24 July 2018

Identifiers

Local EPrints ID: 422960
URI: http://eprints.soton.ac.uk/id/eprint/422960
ISSN: 1559-128X
PURE UUID: b39b34d6-ed3f-4dff-b945-83cd3b8e8e89
ORCID for Huaiqin Lin: ORCID iD orcid.org/0000-0002-9805-4570
ORCID for Johan Nilsson: ORCID iD orcid.org/0000-0003-1691-7959

Catalogue record

Date deposited: 08 Aug 2018 16:30
Last modified: 07 Oct 2020 05:05

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Contributors

Author: Junhua Ji
Author: Huaiqin Lin ORCID iD
Author: Raghuraman Sidharthan
Author: Daryl Ho
Author: Yanyan Zhou
Author: Johan Nilsson ORCID iD
Author: Seongwoo Yoo

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