Ultrashort pulse generation and synchronisation in self-modelocked vibronic lasers
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This thesis is concerned with the generation of ultrashort pulses from vibronic lasers. The two laser active materials used in the course of the work were Ti:sapphire and Cr:LiSAF. A self-modelocked Ti:sapphire laser has been described which generated pulses as short as 2ps, tunable over the wavelength range 730 - 850nm. The average output power was 400mW corresponding to a peak pulse power of 1kW. Using a prism sequence to implement intracavity dispersion-compensation resulted in the generation of near-transform limited pulses as short as 53fs with a peak pulse power of ~100kW. Two initiation techniques have been developed for the generally non-self-starting self- modelocking process, based upon intracavity insertion of either a regeneratively driven acousto-optic modulator or a solid-state saturable absorber. A cw Cr:LiSAF laser pumped by the 476.5nm line of the argon-ion laser output, was demonstrated; this generated a maximum output power of 300mW with a slope efficiency of 20% at 825nm. A dispersion-compensated self-modelocked Cr:LiSAF laser has been described that generated pulses as short as 45fs over the tuning range 770-910nm. The peak pulse power generated was 40kW. The phase noise of a modelocked Ti: sapphire laser has been reduced by referencing the cavity frequency to an ultrastable crystal oscillator. The phase noise of the frequency locked laser was 410fs (100-500Hz), 305fs (500Hz-5kHz) and 263fs (5-50kHz). By referencing two modelocked Ti:sapphire lasers to a common crystal oscillator two independently tunable pulse sequences with a relative timing jitter of ~1ps have been generated. A novel laser based upon a single Ti:sapphire gain element generating synchronised pulses at two different wavelengths has been demonstrated. Cross-correlation data recorded between the two output pulse sequences indicated a relative timing jitter of 26fs.
Thesis, PhD Doctor of Philosophy
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