Ultrashort pulse generation and synchronisation in self-modelocked vibronic lasers

Abstract

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.