Supercontinuum pulse measurement by molecular alignment based cross-correlation frequency resolved optical gating.

We demonstrate that complex supercontinuum and few-cycle ultrashort laser pulses can be fully characterized by using a cross-correlation frequency-resolved optical gating with molecular alignment induced birefringence functioned as a gate. The temporal envelope and phase of the broadband supercontinuum pulse are retrieved by the principal component generalized projection algorithm. This technique shows advantages without phase-matching constraint that may limit the measurable spectral bandwidth, experimental robustness in operating through the whole transparent spectral region of the molecular gases, and intensity sensitivity to measure weak pulses which is inherited from the intrinsic linear process in recording the molecular birefringence induced polarization spectroscopy. Experimental measurements of a few-cycle pulse in the visible region of 525-725 nm confirm that the molecular alignment gating supports a full field characterization of the ultrashort pulse around 10 fs in duration.