The Characterization of Pulse Front Tilt and Spatial Dispersion in 800 NM Femtosecond Lasers

Abstract

<p> This thesis presents a study of diagnostics of pulsed laser systems. Two simple and cost effective devices are constructed that measure common spatio-temporal distortions. The first is a spectrally-resolved knife-edge (SRKE) for spatially and spectrally resolving a laser beam, which enables spatio-temporal distortions to be measured. The second is an interferometric autocorrelation taken with a 2-photon diode. A lens is used to focus light from the entire cross section of the beam onto the diode. By scanning the diode through the focus, the effects of pulse-front-tilt on focused beam pulse durations can be measured. These techniques are compared with current theoretical models, and with each other, to establish their reliability and practicality, as well as the reliability of the commercial techniques. SRKE is found to be highly sensitive to spatial and angular dispersion, and also able to measure the frequency gradient, although not as precisely. Interferometric autocorrelation is only able to resolve effects on duration. It can detect the presence of significant spatio-temporal distortion, but several scans must be taken as a function of distance from the lens, through the focus.</p> <p> A commercially built GRENOUILLE was also tested on pulses compressed with a hollow-capillary-prism pulse compressor. Compression of 800 nm, 50 fs pulses to less than 19 fs was achieved with an overall transmission efficiency of 33%. With further work, efficiency could be increased, and pulse duration decreased.</p>