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Type: Theses
Title: Development of dual-wavelength pumped mid-infrared fibre laser
Author: Henderson-Sapir, Ori
Issue Date: 2015
School/Discipline: School of Physical Sciences
Abstract: There is an urgent need for efficient and compact sources of coherent mid-infrared wavelength radiation (3-5 μm). Cost-effective and bright mid-infrared sources will lead to exciting new sensing applications, ranging from the remote sensing of greenhouse gases, such as CO₂ and methane, to analysis of trace gases in exhaled breath for disease marker identification. The last decade has seen a continuing increase in the output power of various types of mid-infrared sources, such as optical parametric oscillators and amplifiers, quantum cascade lasers and fibre lasers. However, advances in brightness, efficiency, peak power and tunability are still necessary for many applications. In this thesis, we describe a new concept for a fibre laser based on Er³⁺ doped ZBLAN glass that operates in the mid-infrared with lasing centred around 3.5 μm. We used a novel dual-wavelength pumping (DWP) scheme to achieve world-leading efficiency for this material and an output power of 260 mW. The DWP technique uses long-lived excited states in our Er³⁺ ion doped ZBLAN glass gain medium to improve the Stokes efficiency. A low power, 985 nm pump source excites ions from the ⁴I₁₅ ̷₂ ground state to the long lived ⁴I₁₁ ̷₂ state. A large fraction of the ion population can be stored in this level because of its long lifetime, creating a \virtual ground state." A concurrent 1973 nm pump source is then used as the main pump source. This pump excites the ions further to the upper laser level ⁴F₉ ̷₂. Post lasing, the 1973 nm pump cycles the ions between the \virtual ground state" at ⁴I₁₁ ̷₂ and the ⁴F₉ ̷₂ level. The first pump at 985 nm maintains the population in the “virtual ground" as this population is diminished by spontaneous emission and energy-transfer processes, which eject ions from the lasing cycle. In this thesis, we review the literature and the current state-of-the-art in mid-infrared fibre lasers. An overview of the spectroscopic properties of Er³⁺:ZBLAN relevant to mid-infrared operation is presented. The difficulties and issues associated with the creation of mid-infrared radiation are discussed and our spectroscopic investigations of ZBLAN glass and glass fibres are summarised. Multiple wavelengths were used as pump sources for our DWP laser. Our investigation of the optimal wavelength for the DWP technique and the development of suitable sources is described as well. The 3.5 μm laser system is discussed, including the full characterisation of the laser. The thesis is concluded with a summary of the results and an outlook for the future.
Advisor: Ottaway, David J.
Munch, Jesper
Dissertation Note: Thesis (Ph.D.) -- University of Adelaide, School of Physical Sciences, 2015.
Keywords: dual-wavelength pumping
fibre laser
Provenance: Copyright material removed from digital thesis. See print copy in University of Adelaide Library for full text.
This electronic version is made publicly available by the University of Adelaide in accordance with its open access policy for student theses. Copyright in this thesis remains with the author. This thesis may incorporate third party material which has been used by the author pursuant to Fair Dealing exceptions. If you are the owner of any included third party copyright material you wish to be removed from this electronic version, please complete the take down form located at:
DOI: 10.4225/55/58ae25b757fcd
Appears in Collections:Research Theses

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