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This thesis is concerned with the characterisation of sub-millimetre sized solid-state lasers. These 'microchip lasers' are examined in two forms; one as monolithic devices where the dielectric mirrors forming the laser cavity are directly deposited onto two near parallel faces of the laser gain crystal, and the second where the microchip gain material is used in combination with a nonlinear crystal to form a composite device. A range of neodymium doped crystals, operating continuous wave and in gain-switched mode at 1064nm, are compared as potential microchip laser gain materials, including Nd:YVO₄, Nd:YOS, Nd:SFAP and Nd:SVAP. With the exception of Nd:SVAP, slope efficiencies exceeding 40% and thresholds of less than 100mW were measured for all these lasers. A comparison of the 1064nm and 1342nm transitions in Nd:YVO₄ is also carried out showing similar performance for both transitions. The formation of the cavity within these monolithic lasers is described in detail, in particular for the thermal and gain guiding effects in Nd:YVO₄. Both analytical and numerical modelling of these effects are compared with experimental measurement of the cavity formation. When used in conjunction with a saturable absorber, these sub-millimetre sized lasers can be used to produce short, high-intensity pulses. This is demonstrated using Cr:YAG as a saturable absorber for Nd:YVO₄ at 1064nm to produce pulses as short as 1.38ns and peak powers of up to 1kW, and V:YAG to Q-switch Nd:YVO₄ at 1342nm to produce pulses with durations as short as 9.5ns and peak powers up to 360W. Active control for generating pulses is also demonstrated using a novel range of deflective Q-switches. These low cost, low loss, compact devices produced pulses of up to 12kW peak power and pulses duration of less than 1.1ns on demand. The continuous wave, intracavity frequency doubling of the three main ND³⁺ transitions, to give red, green and blue light is described. Up to 220mW of green light, with an efficiency approaching 40%, 33mW of blue light and 10mW of single-frequency red light were produced.
Thesis, PhD Doctor of Philosophy
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