Chromium:Lithium strontium aluminum hexafluoride chirped pulse amplification system for femtosecond white light nonlinear spectroscopy

This dissertation reports time-resolved measurements of the nonlinear transmission spectra of organic dye solutions. The reverse saturable absorption (RSA) of these organic dyes in the visible and near infrared was measured using a femtosecond excitation at a wavelength of 425 nm and a temporally delayed white light continuum probe. These RSA materials have attracted attention due to their usefulness in optical limiting devices. Knowledge of the dynamics of the nonlinear response along with the spectral dependence is important in order to determine the range of operation of a given material and to properly model the level structure and lifetimes. To achieve these experimental results, we developed a femtosecond white-light source based on an argon ion pumped, Kerr lens modelocked Ti:sapphire oscillator followed by a Cr:LiSAF regenerative amplifier producing millijoule level, 150 fs pulses around 850 nm. These single pulses are then split to generate a second harmonic (SH) at 425 nm and a femtosecond continuum extending from 400nm to 800nm that are used as the pump and probe respectively in a standard pump-probe geometry. The SH is produced in a thin {dollar}beta{dollar}-Barium Borate crystal and the continuum is produced by focusing the 850 nm light into a water cell. This results in up to 50 {dollar}mu{dollar}J of 425 nm pump and 3 {dollar}mu{dollar}J of probe in the spectral range from 800 nm to 400 nm. These pulses have been used to temporally resolve the nonlinear spectra of several organic solutions including zinc tetra (p-methoxyphenyl) tetrabenzporphyrin, lead phthalocyanine, and silicon naphthalocyanine with subpicosecond resolution, up to delays of several nanoseconds.