PROPAGATION OF INTENSE, ULTRASHORT LASER-PULSES THROUGH METAL VAPOR -REACTION-LIMITED BEHAVIOR FOR SINGLE PULSES

Propagation of intense, ultrashort laser pulses through self-induced u nderdense aluminum plasmas is examined at intensity levels of as high as 5 X 10(17) W/cm(2). Observations of the on-axis transmitted portion of the incident pulse are consistent with optical-field ionization an d subsequent plasma refraction. A novel application of frequency-resol ved optical gating provides measurement of time-resolved spectra, givi ng amplitude and phase information of the transmitted laser waveform. At high enough incident intensity the transmitted energy is reduced to the 1% level, the short-wavelength extent of the complex spectra can be downshifted by as much as 19% from the incident wavelength, and the duration of the transmitted laser waveform is noticeably shortened. T he usefulness of the frequency-resolved optical gating diagnostic in s tudying the dynamics of ionization and laser-plasma interactions is de monstrated. (C) 1996 Optical Society of America