OPTICAL-PHASE PERTURBATIONS IN NANOSECOND PULSED AMPLIFICATION AND 2ND-HARMONIC GENERATION

Using an optical heterodyne technique, we have measured the phase evolution of nanosecond laser pulses produced by several different dye-amplifier configurations. Considerable frequency chirping is observed as well as average frequency shifts of a few parts in 10(8). We investigate the dependence of this chirping on the amplifier design and the pump laser to identify the best arrangement for precision measurements. We also report calculations of nonlinear phase shifts in frequency-doubling crystals, which can significantly perturb the laser frequency. Finally, we compare the measured phase evolution of second-harmonic radiation with predictions made from the squared electric field of the fundamental.