When using multimode fibers as high-resolution endoscopes, advanced adaptive optics is needed to overcome the modal dispersion which scrambles the image. Additionally, for non-linear imaging methods, all the wavelengths of a femtosecond laser pulse must be simultaneously focused at the sample plane, with appropriate dispersion compensation, that might vary across the sample area. We investigate the bandwidth of the focused spot for a graded index fiber used as a point scanning imaging device. We demonstrate that with proper compensation for the dispersion of the spatial light modulator this can be <45 nm. We also measure the spectral phase at the sample plane, and demonstrate that this does not vary substantially with spot position.
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