Frequency-domain holography is used to measure ultrafast phase shifts induc
ed either by the nonlinear susceptibility chi(3) of fused silica or by ioni
zation fronts in air over a temporal region of 1 ps with 70-fs resolution i
n a single shot. The use of an imaging spectrometer adds one-dimensional sp
atial resolution to the single-shot temporal measurements. (C) 2000 Optical
Society of America.