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Study of partly quenched highly erbium-doped fibre amplifiers

Study of partly quenched highly erbium-doped fibre amplifiers
Study of partly quenched highly erbium-doped fibre amplifiers
This thesis reports an investigation of concentration quenching dynamics in the high-power regime and discusses a novel technique to get high-energy pulses with high gain by using short pulses on a short, highly-doped, partly-quenched fibre (referred to as the signal fibre amplifier, or fibre under test). The focus is not on the microscopic details of the concentration quenching, but the effects of quenching in the high-energy regime and to minimize its detrimental effects. As such, the results explore the impact of concentration quenching on amplification of high energy pulses at various pulse durations, in order to suppress the detrimental effects of quenching while keeping a short fibre length to limit optical nonlinearities. Erbium doped fibres are the focus in this thesis, due to their versatility, attractive operating wavelength range (e.g., 1.5 – 1.6 µm) and relative “eye-safety”. Some of the work reported in this thesis was carried out in collaboration with Naval Research Laboratory.

The technique discussed in this thesis is based on two key steps: (1) The generation and subsequent absorption of pump energy by the signal fibre amplifier followed by (2) the extraction of energy by the signal pulse. There are two different techniques to optically pump the signal fibre amplifier studied in this thesis, one of them is core-pumping and the second is cladding-pumping, both of which are discussed in detail, including their advantages and disadvantages in the context.

Contrary to the generally held view of poor performance due to quenching dynamics in high concentration erbium fibres, this work demonstrates an efficient extraction of high energy from partly quenched high-concentration erbium doped fibre through amplification of short pulses. Although the quenching degrades the average-power efficiency of the amplifier, the pulse energy can remain high, and the results point to an increasingly promising outcome for shorter signal pulses in the ns to µs-range.

Even at low average-power efficiency, the highest achievable pulse energy is largely unaffected, and reached 9.5 times the intrinsic saturation energy in one erbium fibre, which corresponds to an amplified pulse energy of 0.8 mJ. These results are attributed to the rapid extraction of stored energy, on time scales faster than the quenching dynamics. This shows it is possible to outperform the typical unquenched silica erbium-doped fibres in generation of energy per unit core area and length as well as gain per unit length. Thus, according to these results, signal pulses can be amplified to high-energies (approaching mJ-level) in short highly-erbium-doped fibres designed to reduce nonlinear distortions, at the expense of average-power efficiency.
University of Southampton
Rojas Hernandez, Pablo Gerardo
0917a31d-ce16-4f07-8baa-c9c79c6f175d
Rojas Hernandez, Pablo Gerardo
0917a31d-ce16-4f07-8baa-c9c79c6f175d
Nilsson, Lars
f41d0948-4ca9-4b93-b44d-680ca0bf157b

Rojas Hernandez, Pablo Gerardo (2019) Study of partly quenched highly erbium-doped fibre amplifiers. Doctoral Thesis, 123pp.

Record type: Thesis (Doctoral)

Abstract

This thesis reports an investigation of concentration quenching dynamics in the high-power regime and discusses a novel technique to get high-energy pulses with high gain by using short pulses on a short, highly-doped, partly-quenched fibre (referred to as the signal fibre amplifier, or fibre under test). The focus is not on the microscopic details of the concentration quenching, but the effects of quenching in the high-energy regime and to minimize its detrimental effects. As such, the results explore the impact of concentration quenching on amplification of high energy pulses at various pulse durations, in order to suppress the detrimental effects of quenching while keeping a short fibre length to limit optical nonlinearities. Erbium doped fibres are the focus in this thesis, due to their versatility, attractive operating wavelength range (e.g., 1.5 – 1.6 µm) and relative “eye-safety”. Some of the work reported in this thesis was carried out in collaboration with Naval Research Laboratory.

The technique discussed in this thesis is based on two key steps: (1) The generation and subsequent absorption of pump energy by the signal fibre amplifier followed by (2) the extraction of energy by the signal pulse. There are two different techniques to optically pump the signal fibre amplifier studied in this thesis, one of them is core-pumping and the second is cladding-pumping, both of which are discussed in detail, including their advantages and disadvantages in the context.

Contrary to the generally held view of poor performance due to quenching dynamics in high concentration erbium fibres, this work demonstrates an efficient extraction of high energy from partly quenched high-concentration erbium doped fibre through amplification of short pulses. Although the quenching degrades the average-power efficiency of the amplifier, the pulse energy can remain high, and the results point to an increasingly promising outcome for shorter signal pulses in the ns to µs-range.

Even at low average-power efficiency, the highest achievable pulse energy is largely unaffected, and reached 9.5 times the intrinsic saturation energy in one erbium fibre, which corresponds to an amplified pulse energy of 0.8 mJ. These results are attributed to the rapid extraction of stored energy, on time scales faster than the quenching dynamics. This shows it is possible to outperform the typical unquenched silica erbium-doped fibres in generation of energy per unit core area and length as well as gain per unit length. Thus, according to these results, signal pulses can be amplified to high-energies (approaching mJ-level) in short highly-erbium-doped fibres designed to reduce nonlinear distortions, at the expense of average-power efficiency.

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Published date: September 2019

Identifiers

Local EPrints ID: 447020
URI: http://eprints.soton.ac.uk/id/eprint/447020
PURE UUID: c452f4de-9139-4273-a4df-3d6a8e24b7c6
ORCID for Lars Nilsson: ORCID iD orcid.org/0000-0003-1691-7959

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Date deposited: 01 Mar 2021 17:35
Last modified: 17 Mar 2024 02:47

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Contributors

Author: Pablo Gerardo Rojas Hernandez
Thesis advisor: Lars Nilsson ORCID iD

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