Label-free CARS microscopy through a multimode fiber endoscope

Multimode fibres have recently been employed as high-resolution ultra-thin endoscopes, capable of imaging biological structures deep inside tissue in vivo. Here, we extend this technique to label-free non-linear microscopy with chemical contrast using coherent anti-Stokes Raman scattering (CARS) through a multimode fibre endoscope, which opens up new avenues for instant and in-situ diagnosis of potentially malignant tissue. We use a commercial 125 mu m diameter, 0.29 NA GRIN fibre, and wavefront shaping on an SLM is used to create foci that are scanned behind the fibre facet across the sample. The chemical selectivity is demonstrated by imaging 2 mu m polystyrene and 2.5 mu m PMMA beads with per pixel integration time as low as 1 ms for epi-detection. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement