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Title: Diode-pumped alexandrite laser development and vortex mode generation
Author: Kerridge-Johns, William
ISNI:       0000 0004 7658 3142
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2018
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This thesis is focussed on two aspects of solid-state laser development: optimising and understanding diode-pumped Alexandrite laser performance, and a new laser cavity design for vortex mode generation. Due to its broad wavelength tunability (700nm to 858nm) and excellent physical properties, Alexandrite has a wide range of potential applications from remote sensing to quantum optics. Recent advances in red laser diode-pumping has enabled high power and efficient laser operation. In this work a continuous-wave analytical model of end-pumped Alexandrite lasers was developed and applied to experimental systems. This helped to achieve a record diode-pumped slope efficiency of 54% with 1.2W of output power. A record shortest wavelength (714nm) and broadest tuning range (104nm) was obtained through optimising the crystal temperature between 8 °C and 105 °C. Investigation and new measurements of the properties of Alexandrite gave rules applicable in general to optimising these lasers, along with assessing the fundamental limits to Alexandrite laser efficiency. Optical vortex laser beams have attracted considerable attention from their wide range of applications that cover many areas of science, from optical communications to laser machining to microscopic laser manipulation. Directly generating them from a laser has advantages due to the pure and high power modes that can be generated. In this work an anti-resonant ring was proposed and used to couple two lasers through a shared gain medium. Using one cavity to control the output of the other, first order vortex Laguerre-Gaussian modes of power 9.0W from 24W of input power with high quality (M² = 2.1) were obtained, which had controllable and pure handedness. A second order vortex mode with 4.3W of power was also created. This vortex generation geometry could be applied to any solid-state laser gain medium, which would enable vortex generation across the electromagnetic spectrum.
Supervisor: Damzen, Michael J. Sponsor: Imperial College London
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral