Spatiotemporal beam self-cleaning for high-resolution nonlinear fluorescence imaging with multimode fiber
Nawell Ould Moussa, Tigran Mansuryan, Charles‐Henri Hage, Marc Fabert, Katarzyna Krupa, Alessandro Tonello, Mario Ferraro, Luca Leggio, Mario Zitelli, Fabio Mangini, Alioune Niang, G. Millot, Massimiliano Papi, S. Wabnitz, Vincent Couderc
Abstract
Beam self-cleaning (BSC) in graded-index (GRIN) multimode fibers (MMFs) has been recently reported by different research groups. Driven by the interplay between Kerr effect and beam self-imaging, BSC counteracts random mode coupling, and forces laser beams to recover a quasi-single mode profile at the output of GRIN fibers. Here we show that the associated self-induced spatiotemporal reshaping allows for improving the performances of nonlinear fluorescence (NF) microscopy and endoscopy using multimode optical fibers. 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 efficiency 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 findings by multiphoton fluorescence imaging in both microscopy and endoscopy configurations.