SPECTRAL, TEMPORAL, AND SPATIAL CHARACTERISTICS OF PLASMA-INDUCED SPECTRAL BLUE SHIFTING AND ITS APPLICATION TO FEMTOSECOND PULSE MEASUREMENT

The spectral, temporal, and spatial characteristics of plasma-induced spectral blue shifting in atmospheric-density rare gases were investig ated by a two-color pump-probe technique. When the degree of ionizatio n is less than 1, experiments and theoretical results show that field ionization occurs over a time approximately equal to half the pump-pul se width and that ionization-induced defocusing causes spectral blue s hifting to be spatially dependent. The pulse width of a 147-nm pulse g enerated by four-wave mixing of a femtosecond KrF laser pulse in xenon was determined to be 400 fs by a cross-correlation technique based on plasma defocusing. (C) 1996 Optical Society of America