STED microscopy at the tip of a holographic multimode fibre endoscope

Holographic multimode fibre endoscopes have recently shown their promising potential as a minimally invasive imaging tool, particularly in the field of neurobiology. Currently, their resolution is limited by diffraction, constrained by the relatively low numerical aperture of the multimode fibres used (typically less than 0.4). Overcoming the diffraction-limit barrier would open new possibilities for detailed observation of dendritic spines and their motility in-vivo. In this presentation we demonstrate pulsed STED microscopy delivered through a holographic multimode fibre endoscope. We show resolution improvements over 3-fold of the diffraction limit. Moreover, we discuss and showcase its applicability to bio-imaging.