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Ultra-low NA step-index large mode area Yb-doped fiber with a germanium doped cladding for high power pulse amplification

Ultra-low NA step-index large mode area Yb-doped fiber with a germanium doped cladding for high power pulse amplification
Ultra-low NA step-index large mode area Yb-doped fiber with a germanium doped cladding for high power pulse amplification

High concentration rare earth doped, large mode area (LMA) step-index fibers, which feature a very high cladding absorption per unit length at the pump wavelength, high efficiency, and excellent beam quality, are ideal for high power pulsed fiber lasers/amplifiers where large effective mode areas and short device lengths are crucial in order to reduce detrimental nonlinear effects associated with high peak power operation. In this Letter, we realize low numerical aperture (NA) high absorption fibers, simply by employing a germanium (Ge)-doped cladding rather than a pure silica cladding to offset the high refractive index associated with using a high concentration of ytterbium (Yb) in the core. This approach allows us to separate the two inter-linked fiber design parameters of pump absorption and NA in a step-index fiber. Using a conventional modified chemical vapor deposition process combined with solution doping, a low NA (0.04), LMA (475 μm2) silica fiber is fabricated with a cladding absorption value of >20 dB=m, which is the highest value among LMA step-index fibers withNA<0.06 so far reported to the best of our knowledge. The fabricated Yb-doped fiber was tested in a high-power picosecond amplifier system and enabled the generation of 190 ps laser pulses with a 101 μJ pulse energy and 0.5MW peak power at an average power of 150 W.

0146-9592
3828-3831
Sidharthan, Raghuraman
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Lin, Di
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Lim, Jang Jie
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Li, Huizi
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Lim, Serene Huiting
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Chang, Chen Jian
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Seng, Yue Men
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Chua, Song Liang
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Jung, Yongmin
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Richardson, David J.
ebfe1ff9-d0c2-4e52-b7ae-c1b13bccdef3
Yoo, Seongwoo
dcabaaed-490b-4024-8271-ea8048653faf
Sidharthan, Raghuraman
3a64468c-0706-4cd6-8fab-2fbe65392c4b
Lin, Di
d858c2c7-6eab-49d8-87e7-6b71d9bad013
Lim, Jang Jie
59668283-9624-4eed-ac5c-26557a34e284
Li, Huizi
fd7a494d-8a38-4d1f-b734-492897da9823
Lim, Serene Huiting
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Chang, Chen Jian
1b1e147a-c68b-4bf7-8070-f5e1e1618456
Seng, Yue Men
3845ce7a-80b3-4a65-afe6-db45e52694d3
Chua, Song Liang
0d305f5f-2604-4f17-a141-a4454457aaae
Jung, Yongmin
6685e51e-be47-4c96-8c4b-65aee3b5126d
Richardson, David J.
ebfe1ff9-d0c2-4e52-b7ae-c1b13bccdef3
Yoo, Seongwoo
dcabaaed-490b-4024-8271-ea8048653faf

Sidharthan, Raghuraman, Lin, Di, Lim, Jang Jie, Li, Huizi, Lim, Serene Huiting, Chang, Chen Jian, Seng, Yue Men, Chua, Song Liang, Jung, Yongmin, Richardson, David J. and Yoo, Seongwoo (2020) Ultra-low NA step-index large mode area Yb-doped fiber with a germanium doped cladding for high power pulse amplification. Optics Letters, 45 (14), 3828-3831. (doi:10.1364/OL.396157).

Record type: Article

Abstract

High concentration rare earth doped, large mode area (LMA) step-index fibers, which feature a very high cladding absorption per unit length at the pump wavelength, high efficiency, and excellent beam quality, are ideal for high power pulsed fiber lasers/amplifiers where large effective mode areas and short device lengths are crucial in order to reduce detrimental nonlinear effects associated with high peak power operation. In this Letter, we realize low numerical aperture (NA) high absorption fibers, simply by employing a germanium (Ge)-doped cladding rather than a pure silica cladding to offset the high refractive index associated with using a high concentration of ytterbium (Yb) in the core. This approach allows us to separate the two inter-linked fiber design parameters of pump absorption and NA in a step-index fiber. Using a conventional modified chemical vapor deposition process combined with solution doping, a low NA (0.04), LMA (475 μm2) silica fiber is fabricated with a cladding absorption value of >20 dB=m, which is the highest value among LMA step-index fibers withNA<0.06 so far reported to the best of our knowledge. The fabricated Yb-doped fiber was tested in a high-power picosecond amplifier system and enabled the generation of 190 ps laser pulses with a 101 μJ pulse energy and 0.5MW peak power at an average power of 150 W.

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Manuscript-Optics Letters Final 20200427 - Accepted Manuscript
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Accepted/In Press date: 28 May 2020
Published date: 6 July 2020
Additional Information: Funding Information: Engineering and Physical Sciences Research Council (EP/P030181/1); National Hub in High Value PhotonicManufacturing (EP/N00762X/1). Publisher Copyright: © 2020 Optical Society of America.

Identifiers

Local EPrints ID: 442348
URI: http://eprints.soton.ac.uk/id/eprint/442348
ISSN: 0146-9592
PURE UUID: 2d342a5c-eef9-48d5-9103-75bcc6401b13
ORCID for Di Lin: ORCID iD orcid.org/0000-0001-5025-9051
ORCID for Yongmin Jung: ORCID iD orcid.org/0000-0002-9054-4372
ORCID for David J. Richardson: ORCID iD orcid.org/0000-0002-7751-1058

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Date deposited: 14 Jul 2020 16:30
Last modified: 17 Mar 2024 05:43

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Contributors

Author: Raghuraman Sidharthan
Author: Di Lin ORCID iD
Author: Jang Jie Lim
Author: Huizi Li
Author: Serene Huiting Lim
Author: Chen Jian Chang
Author: Yue Men Seng
Author: Song Liang Chua
Author: Yongmin Jung ORCID iD
Author: Seongwoo Yoo

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