Here, we demonstrate two-photon excitation imaging of fluorescent beads through a multimode optical fiber. We show that our method maintains the advantages of two-photon excitation microscopy compared to single-photon excitation such as reduced photo-bleaching, deeper penetration depth and sectioning capability. Our method is based on time-gated digital phase conjugation, which allows the generation of focused pulses on the other side of a multimode fiber. To acquire an image, the focused femtosecond pulse is scanned in a three-dimensional mesh, producing two-photon excitation on each spatial location of the sample. By collecting the fluorescence through the fiber, a 3D two-photon image is reconstructed.
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Edgar E. Morales Delgado, Demetri Psaltis, Christophe Moser, "Two-photon excitation endoscopy through a multimode optical fiber," Proc. SPIE 9717, Adaptive Optics and Wavefront Control for Biological Systems II, 97171E (15 March 2016);