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Pulsed laser sources utilising liquid crystals as intracavity modulators

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posted on 28.03.2022, 09:18 authored by Christoph Wieschendorf
A range of techniques for fabricating optical waveguides in actively doped media has previously been developed. Macquarie University has specialised in the femtosecond laser direct-write technique, a flexible method that enables the inscription of three-dimensional structures into transparent media. By inscribing depressed-cladding waveguides into doped fluoride glass chips, continuous-wave (CW) lasers with extraordinarily large fundamental mode-field diameters have been realised. However, in order to generate optical pulses with high peak-power levels, an actively controlled intracavity loss modulator would be required. While the use of bulk acousto-optic modulators has been demonstrated, the waveguide chip laser architecture is best utilised with a modulator that is compatible with a monolithic and integrated design. In the present work, a novel type of a liquid-crystal based transducer was utilised as an intracavity loss modulator that can be integrated onto the laser chip, opening up the possibility of realising monolithic miniaturised actively Q-switched high peak-power laser sources. This liquid crystal cell was initially developed by our collaborator in the context of distributed sensor networks and therefore its switching behaviour on a microsecond to sub-microsecond timescale had to be studied first. Next, the cell was employed as an active Q-switch in an ytterbium glass waveguide laser, resulting in peak power levels approaching 100 W. Further,the use of this technology in laser chips based on polarisation-maintaining waveguides in crystalline materials was investigated in the visible spectral region, and this approach was also extended towards the mid-infrared spectral region with the aim of utilising nonlinear optical effects in chalcogenide fibres to generate broadband radiation in the important mid-infrared fingerprint region of the optical spectrum. Finally, the feasibility of using the liquid-crystal modulator as a mode-locking device in fibre lasers was investigated and a fibre laser that can be switched between mode-locked, Q-switched and CW operation was demonstrated.


Table of Contents

1. Motivation -- 2. Background - theory and experimental methods -- 3. Liquid crystal cell -- 4. Liquid crystal Q-switched waveguide chip lasers -- 5. Compact Q-switched waveguide laser - an application -- 6. Summary and future work -- List of publications -- References.


Bibliography: pages 165-191 Empirical thesis.

Awarding Institution

Macquarie University

Degree Type

Thesis PhD


PhD, Macquarie University, Faculty of Science and Engineering, Department of Physics and Astronomy

Department, Centre or School

Department of Physics and Astronomy

Year of Award


Principal Supervisor

Alexander Fürbach

Additional Supervisor 1

Simon Gross

Additional Supervisor 2

David J. Spence


Copyright Christoph Wieschendorf 2018. Copyright disclaimer: http://mq.edu.au/library/copyright




1 online resource (xviii, 191 pages) colour illustrations

Former Identifiers

mq:71283 http://hdl.handle.net/1959.14/1272711