Characterization of a femtosecond laser and its application to the study of breakdown in dielectric thin films

A femtosecond Ti:sapphire laser-amplifier chain was designed, developed and characterized. A 10-fs Kerr lens modelocked Ti:sapphire laser seeds a multipass amplifier that generates 20-fs pulses of ∼250 μJ energy.; A simple and inexpensive new technique called PICASO that uses only correlations and the pulse spectrum for complete characterization of the phase and amplitude of femtosecond pulses was developed and used to characterize the output of the oscillator.; Evolution of the pulse spectrum under the envelope of two different quasi-periodic self-modulated regimes of the Ti:sapphire oscillator were studied. A theory to explain the pulse evolution in these regimes is developed. Stabilization of the modulations is demonstrated.; The radius dependent dispersion of high numerical aperture microscope objectives is accurately characterized and its effect on the temporal distribution of 10-fs pulses at the focus is studied. Peak intensities approaching 10 14 W/cm2 are demonstrated with the oscillator.; Dielectric breakdown of wide bandgap dielectric thin films with femtosecond pulses is investigated. The breakdown is explained by a model that takes into account multiphoton absorption, impact ionization and local intensity enhancements due to interference effects in the films. Incubation is found to lower the damage threshold under multiple pulse exposure. Time-resolved pump-probe spectroscopy on the sample excited close to the damage threshold reveals the various relaxation time scales for the electron plasma and indicates the creation of long lived trap states that are the probable cause of the observed incubation.