Pulse retrieval from cropped FROG traces

Summary form only given. Frequency Resolved Optical Gating (FROG) is a technique to measure ultrashort laser pulses [1]. It requires the measurement of a spectrally resolved autocorrelation, in the case of SHG FROG by using non-collinear second harmonic generation. The pulse amplitude and phase can then be retrieved numerically from the measurement.Classically, the so-called FROG trace must not be cropped [2]. This means that the measurement window in frequency and delay must contain the complete signal. In some cases fulfilling this requirement is a technical challenge due to the length of the delay line or the frequency range of the spectrometer. In other cases it can be a fundamental challenge, e.g. when harmonic and fundamental spectrum overlap. In this work we demonstrate that it is possible to retrieve the pulse amplitude and phase from FROG traces that are cropped either on the frequency axis, or the delay axis, or both. We further discuss which requirements have to be met to allow for a sufficient retrieval.