Two-dimensional spectral shearing interferometry resolved in time for ultrashort optical pulse characterization

We present a new scheme for coherent measurement of ultrashort optical pulses that relies on spectral shearing interferometry combined with all-optical time gating. The spectral phase is encoded along a temporal coordinate resulting in a two-dimensional (2D) self-referenced and self-calibrating set of data. The method works without time delay between the two interfering signals. The pulse amplitude and phase are reconstructed with a high signal-to-noise ratio using a direct algorithm that applies a Fourier transform (FT) to the 2D recorded interference pattern. Characterization of low-energy, high-repetition-rate femtosecond pulses of various shapes and validation of a single-shot operation are reported.