Spatiotemporal beam self-cleaning for high-resolution nonlinear fluorescence imaging with multimode fibres

TL;DR

This paper demonstrates that spatiotemporal beam self-cleaning in multimode fibres enhances nonlinear fluorescence imaging by increasing brightness, improving resolution, and enabling broadband supercontinuum generation for advanced microscopy and endoscopy.

Contribution

It introduces the use of spatiotemporal beam self-cleaning in multimode fibres to significantly improve nonlinear fluorescence imaging performance.

Findings

Enhanced two- and three-photon imaging resolution.

Temporal pulse shortening increases peak power and imaging efficiency.

Effective supercontinuum generation for broadband fluorescence imaging.

Abstract

Beam self-cleaning (BSC) in graded-index (GRIN) multimode fibres (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 fibres. Here we show that the associated self-induced spatiotemporal reshaping allows for improving the performances of nonlinear fluorescence microscopy and endoscopy using multimode optical fibres. 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 generation is well-suited for large-band nonlinear fluorescence imaging in visible and infrared domains. We substantiated our findings by multiphoton fluorescence imaging in both microscopy and endoscopy configurations.