title: Enhanced two-photon excitation through optical fiber by single-mode propagation in a large core.
abstract: Multiphoton excitation through optical fibers is limited by pulse broadening caused by self-phase modulation. We show that for short fiber lengths (approximately 2 m) two-photon excitation efficiency at the fiber output can be substantially improved by single-mode propagation in a large-area multimode fiber (10-microm core diameter) instead of a standard 5.5-microm core fiber. Measurements and numerical simulations of postfiber spectra and pulse widths demonstrate that the increase in efficiency is due to a reduction of nonlinear pulse broadening. Single-mode propagation in a large-core fiber is thus suitable for multiphoton applications for which pulse recompression is not possible at the fiber end.
authors.affiliation: Bell Laboratories, Lucent Technologies, Murray Hill, New Jersey 07974, USA. fritjof@mpimf-heidelberg.mpg.de
authors.forename: Fritjof
authors.initials: F
authors.lastname: Helmchen
authors.forename: David W
authors.initials: DW
authors.lastname: Tank
authors.forename: Winfried
authors.initials: W
authors.lastname: Denk