To the right is a pulse with cubic spectral chirp. We like to call this FROG trace “The Kiss.” As with the case when cubic spectral chirp is added to the pulse, ringing occurs in the time domain representation of the pulse. In an autocorrelation, this ringing shows up as wings.

Pictured on the left is the screen capture of VideoFROG FROG scan measuring a pulse with fourth, fifth, and sixth order components of the spectral phase. In addition, the center portion of the spectrum is removed. The main portion of the pulse is about 70 fs wide while the pedestal spans about 1 ps. The ringing on the left portion of the central peak is indicative of odd order phase.

This pulse has large amounts of cubic and quartic spectral chirp--enough to influence the structure of the pulse spectrum. Notice that to the right of the central pulse, there is some ringing, and to the left, the ringing has a higher frequency. Also notice that the base of the pulse spans 2 ps!

To generate this pulse, so much quartic chirp was added that the pulse shaper aliased the phase, causing a highly structured spectrum and a poorly defined spectral phase. The time domain pulse is comprised of three primary pulses that range over about 1.5 ps. The narrowest of the pulses is about 25 fs in width.