Abstract

In this talk, we present experimental and theoretical results on ultrashort high-harmonic generation in gases, using a high peak-power Ti:sapphire laser with 25fs pulsewidth. In these experiments, we focus the laser pulses into a gas cell to generate the high harmonics, and use a grazing-incidence soft-x-ray spectrometer to observe the soft x-ray emission. The bandwidth of the laser pulses is 32nm, centered at a wavelength of 805nm, and the laser system can provide up to 70mJ of energy per pulse at a 10Hz repetition rate.[1] These experiments are approaching a new regime in laser-matter interactions, since for our excitation pulses (10 optical cycles FWHM), at the half-maximum intensity of the temporal pulse envelope the laser intensity changes by more than 25% during a single cycle. This challenges the adiabatic assumption, which presupposes that the atomic dipole moment undergoes quasi-periodic motion from cycle to cycle, with no dependence on the history of the pulse.

© 1996 Optical Society of America