End-pumped solid-state lasers.

Abstract

This dissertation consists of four sections, with the focus on near- and mid-infrared lasers using Yttrium Lithium Fluoride (YLF) crystals doped with various rare-earth ions as a gain medium. As introduction a general overview of the concepts pertaining to end-pumped solid- state lasers are presented. The basic principles, components and operation of lasers are discussed. Stimulated emission, laser gain media, pump sources and pump geometries are elaborated upon. Three-, four-, quasi-three- and quasi-four-level laser schemes are described. Finally, the advantages and disadvantages of end-pumping as opposed to side-pumping schemes for solid-state lasers are discussed. Thereafter, the design and results of a high-powered diode-end-pumped Nd:YLF laser is presented. In conjunction with previously demonstrated methods, the thermal fracture issues of Nd:YLF were addressed by utilizing the natural doping gradient along the boule of the crystal. This, in addition to a novel crystal mounting technique, resulted in the highest reported output power from a diode-end-pumped Nd:YLF laser as well as record pumping powers. In the third section, a compact Ho:YLF oscillator-ampli er system is reported. The novel setup utilised the unpolarised pump power from a bre-laser e ciently by using the pump light transmitted by the oscillator crystal to pump the ampli er crystal, which produced 21.3mJ at 1 kHz, with an M2 better than 1.1. Lastly, the conclusion is drawn that YLF as a host material can be used in a highly successful manner for high-power applications. Additionally, the novel pumping scheme implemented in the Ho:YLF oscillator-amplifier has been shown to be scalable by a subsequent system which delivered record performance.