Directly measuring the spatio-temporal electric field of ultrashort pulses in and near a focus

A new high-spectral-resolution and experimentally simple spectral-interferometry method for measuring the intensity and phase of potentially complicated ultrashort pulses, which we call SEA TADPOLE is introduced. This SEA TADPOLE can exhibit spectral super-resolution. Other notable properties of SEA TADPOLE are that its entrance is an optical fiber with a core size of only a few mum (or less) and SEA TADPOLE is very sensitive, requiring only a few thousand photons for a measurement. For these reasons, SEA TADPOLE can measure a tiny region of a collimated, diverging, or converging beam, and it can measure a tightly focused beam.