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

Using an optical heterodyne technique, we have measured the phase evol ution of nanosecond laser pulses produced by several different dye-amp lifier configurations. Considerable frequency chirping is observed as well as average frequency shifts of a few parts in 10(8). We investiga te the dependence of this chirping on the amplifier design and the pum p laser to identify the best arrangement for precision measurements. W e also report calculations of nonlinear phase shifts in frequency-doub ling crystals, which can significantly perturb the laser frequency. Fi nally, we compare the measured phase evolution of second-harmonic radi ation with predictions made from the squared electric field of the fun damental.