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Title: Development of pulsed diode pumped solid state lasers in the bounce amplifier geometry
Author: Arbabzadah, Emma
ISNI:       0000 0005 0732 2966
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2014
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The work in this thesis focuses on the development of diode pumped solid state (DPSS) lasers, constructed using the bounce amplifier geometry. The bounce amplifier geometry employs a simple side pumping scheme using diode bars and stacks, leading to an efficient and compact system. The laser mode is total internally reflected at the pump surface, spatially averaging gain and thermal non-uniformities giving potential for excellent beam quality from these systems. In this thesis, novel pulsed laser sources based on the 1μm transition of the Nd3+ ion and the 3μm transition of the Er3+ ion are developed, and investigated both experimentally and numerically. An acousto-optically Q-switched Nd:YVO4 laser operating at 1064nm with ultra-high gain (~105) is developed, and using a novel pulse control technique is demonstrated to provide better performance and greater flexibility of the pulsing parameters. Pulsed lasers are useful for many applications, including industrially in laser micromachining and laser marking, where having greater control of laser parameters (e.g. pulse repetition rate, pulse duration and pulse energy) enhances the usefulness of the laser significantly. A problem associated with Q-switching of a high-gain laser system is the difficulty in obtaining clean, single pulse operation from very high (~1MHz) to low (~1kHz) repetition rates. The pulse control technique demonstrated for the first time in this work addresses this issue. The technique uses a secondary laser cavity to control the gain of a primary laser cavity. Prior to implementation of the technique, laser breakthrough occurred at low repetition rates due to the excessive gain and single pulsed operation was not possible below 150kHz. Using the pulse control technique, single pulsed operation was obtained from 800kHz down to 1kHz, with good beam quality across the range, as well as the ability for pulse energy control demonstrated. The development of 3μm laser sources, using Er3+ doped materials is presented. Lasers operating at 3μm are useful directly in applications in medicine and dentistry due to being near the peak of water absorption, as well as indirectly as pump sources for optical parametric generation for production of tuneable mid-IR radiation for spectroscopy, security and defence, and remote sensing applications. In this work, a comparison of the Er:YAG and Er:YSGG laser materials operating at the 3μm transition is undertaken showing superior performance from the less commonly used Er:YSGG material. Different cavity designs are subsequently investigated using the Er:YSGG laser material and an electro-optically Q-switched Er:YSGG laser at 3μm is developed. Numerical modelling of the erbium laser is presented providing greater understanding of laser operation in this complex laser system.
Supervisor: Damzen, Michael Sponsor: Engineering and Physical Sciences Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral