Temporal and phase measurements of ultraviolet femtosecond pulses at 200 nm by molecular alignment based frequency resolved optical gating

We demonstrate that the temporal profile and phase of a weak ultraviolet femtosecond pulse around 200 nm can be measured by molecular alignment based cross-correlation frequency resolved optical gating technique. This technique employs the impulsive alignment of gaseous molecules as gate function and exhibits the advantage of no phase-matching constraint and applicability to pulses at various wavelengths. Simultaneous measurements of near-infrared and ultraviolet pulses are demonstrated. Its agreements with the independent spectral phase interferometry for direct electric field reconstruction and second-order auto-correlation measurements confirm that the molecular alignment gating is a robust technique for ultrashort pulse diagnosis.