Temporal diffraction in a chirped-pulse amplification system

Pulse shaping has received considerable attention for manipulating ultrashort pulses. In most cases the pulse shaper is linear, i.e., the amplitude and/or phase masks do not depend on the intensity of the pulse. Recently, nonlinear pulse shapers—ones in which the pulse-shaping effect is a function of the laser intensity—have been demonstrated.1,2 Here we report nonlinear pulse shaping by using two chirped pulses propagating in a laser gain medium. The unique feature of our experiment is that we simultaneously resolve temporal and spectral behaviors of the pulses by using a spectrometer-streak-camera combination. We show that additional frequencies are generated as a result of nonlinear interaction in the gain medium, and the pulses that carry the new frequencies are those created by temporal diffraction as a result of pulse shaping.