Abstract

Ultrashort light pulses are an attractive tool to combine high spatial resolution and high temporal resolution. Fundamental limits of such uses, e.g., in laser scanning microscopes, are given by the space-time distribution of the pulse intensity in the focal plane of a lens (system). In the framework of geometrical optics it was shown in Ref. 1 that tight focusing can lead to a significant temporal broadening of the pulses in the focal spot. This is caused by the aperture-dependent difference between phase and pulse fronts behind the lens (experimentally observed in Ref. 2) and by group velocity dispersion of the lens material. To determine the coupled temporal and spatial behavior we performed a Fourier-optical treatment of the focusing of an ultrashort light pulse by a single, thin lens, i.e., we solved the corresponding diffraction problem.³

© 1992 Optical Society of America