Characterization of sub-10-fs pulse focusing with high-numerical-aperture microscope objectives

Dispersion precompensation with a prism sequence and a third-order dispersi on mirror resulted in negligible broadening of sub-10-fs pulses at subwavel ength spot sizes when the pulses were focused with microscope objectives an d moderate apertures. At larger apertures, lens chromaticity and spherical aberration led to an effective pulse broadening of up to 1.3x, depending on the aperture size and the detector position. The data suggest that intensi ties exceeding 10(14) W/cm(2) can be produced directly from femtosecond pul se oscillators. (C) 1999 Optical Society of America.