Propagation of intense, ultrashort laser pulses through metal vapor: refraction-limited behavior for single pulses

Abstract

Propagation of intense, ultrashort laser pulses through self-induced underdense aluminum plasmas is examined at intensity levels of as high as 5 × 10¹⁷ W/cm². Observations of the on-axis transmitted portion of the incident pulse are consistent with optical-field ionization and subsequent plasma refraction. A novel application of frequency-resolved optical gating provides measurement of time-resolved spectra, giving 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. The usefulness of the frequency-resolved optical gating diagnostic in studying the dynamics of ionization and laser–plasma interactions is demonstrated.