Spatiotemporal beam self‑cleaning for high‑resolution nonlinear fuorescence imaging with multimode fber

Beam self-cleaning (BSC) in graded-index (GRIN) multimode fbers (MMFs) has been recently reported by diferent research groups. Driven by the interplay between Kerr efect and beam self-imaging, BSC counteracts random mode coupling, and forces laser beams to recover a quasi-single mode profle at the output of GRIN fbers. Here we show that the associated self-induced spatiotemporal reshaping allows for improving the performances of nonlinear fuorescence (NF) microscopy and endoscopy using multimode optical fbers. We experimentally demonstrate that the beam brightness increase, induced by self-cleaning, enables two and three-photon imaging of biological samples with high spatial resolution. Temporal pulse shortening accompanying spatial beam clean-up enhances the output peak power, hence the efciency of nonlinear imaging. We also show that spatiotemporal supercontinuum (SC) generation is well-suited for large-band NF imaging in visible and infrared domains. We substantiated our fndings by multiphoton fuorescence imaging in both microscopy and endoscopy confgurations.

N.O. Moussa, T. Mansuryan, C.H. Hage, M. Fabert, K. Krupa, A. Tonello, M. Ferraro, L. Leggio, M. Zitelli, F. Mangini, A. Niang, G. Millot, M. Papi, S. Wabnitz and V. Couderc, “Spatiotemporal beam self-cleaning for high-resolution nonlinear fluorescence imaging with multimode fibres,”