Guiding and high-harmonic generation of sub-10-fs pulses in hollow-core fibers at 1015 W/cm2

Sub-10-fs laser pulses have been guided in the fundamental transverse mode of a hollow-core fused-silica fiber at intensities of approximate to (1 - 2) x 10(15) W/cm(2). The high resistance of fused silica to damage in the sub-10-fs regime allows stable reproducible operation without degradation of the capillary waveguide. In preliminary experiments, we demonstrate kHz-repetition-rate guided-wave high-harmonic generation in helium down to the 10-nm range. The reported experiments open up the way to realizing high-field interactions with plane-wave excitation at intensity levels in excess of 10(15) W/cm(2) under well-controlled conditions.