Coherent femtosecond pulse shaping for the optimization of a non-linear micro-endoscope.

A flexible multicore fiber bundle is fed by temporally and spectrally shaped femtosecond pulses allowing for the pre-compensation of both chromatic dispersion and non-linear effects encountered in the bundle. We demonstrate that the pulse duration at the fiber bundle output can be significantly reduced in comparison with linear pre-compensation only. The scheme for femtosecond pulse fiber delivery is applied to the optimization of two-photon fluorescence (TPF) imaging. Experiments and calculations show a five-fold improvement of the TPF signal produced at the end of the fiber bundle in comparison with linear pre-compensation. This is applied to the recording, in real time (12 image/s), of TPF laser-scanning images of human colon cells stained with a fluorescent marker. Further optimizations are discussed.