Extending Femtosecond Metrology to Longer, More Complex Laser Pulses in Time and Space

We review several recently developed simple, yet powerful, techniques for the measurement of the complete temporal (and spatiotemporal) intensity and phase of laser pulses up to nanoseconds in length. Spatially encoded arrangement for temporal analysis by dispersing a pair of light e-fields (SEA TADPOLE) is a simple and practical variation of spectral interferometry that can measure pulses as long as ~50 ps with complexities, that is, time-bandwidth products (TBPs) as large as ~100. SEA TADPOLE can also measure the complete spatiotemporal electric field of pulses with femtosecond temporal and submicrometer spatial resolution. Using a train of identical reference pulses, multiple delays for temporal analysis by dispersing a pair of light e-fields (MUD TADPOLE) extends SEA TADPOLE to pulses up to several nanoseconds long with TBPs of ~100 000 or more. Finally, a simple variation of frequency-resolved optical gating (FROG) measures the complete intensity and phase of nanosecond-long laser pulses on a single shot without a reference pulse. It uses a novel approach in which the pulse to be measured is tilted by ~89.9°, so that one side of it precedes the other by over a meter, yielding several nanoseconds of delay without appreciably distorting the pulse in time. This remarkably simple and compact FROG device has no sensitive alignment parameters.