Adaptive Multiphoton Endomicroscope Incorporating a Polarization-Maintaining Multicore Optical Fibre

Paul M. W. French,Jonathan C. Knight,Chris W. Dunsby,Youngchan Kim,Sean C. Warren,Mark A. A. Neil,James M. Stone,Carl Paterson

doi:10.1109/jstqe.2015.2488283

Paul M. W. French, Jonathan C. Knight + Show 6 more

Open Access

https://doi.org/10.1109/jstqe.2015.2488283

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Abstract

We present a laser scanning multiphoton endomicroscope with no distal optics or mechanical components that incorporates a polarization-maintaining (PM) multicore optical fibre to deliver, focus, and scan ultrashort pulsed radiation for two-photon excited fluorescence imaging. We show theoretically that the use of a PM multicore fibre in our experimental configuration enhances the fluorescence excitation intensity achieved in the focal spot compared to a non-PM optical fibre with the same geometry and confirm this by computer simulations based on numerical wavefront propagation. In our experimental system, a spatial light modulator (SLM) is utilised to program the phase of the light input to each of the cores of the endoscope fibre such that the radiation emerging from the distal end of the fibre interferes to provide the focused scanning excitation beam. We demonstrate that the SLM can enable dynamic phase correction of path-length variations across the multicore optical fibre whilst the fibre is perturbed with an update rate of 100 Hz.

Highlights

M ULTIPHOTON microscopy [1] provides inherently optically sectioned images, enabling biochemical structure and activity to be studied in biological tissue [2]–[4], and is increasingly applied in vivo
We have reported an adaptive multiphoton fluorescence endomicroscope implemented with a double-clad PM multicore fibre for the first time that is demonstrated to generate and scan a focused beam at the distal end with no distal optics or mechanical components
We note that our calculations indicate that the PM multicore fibre provides significantly higher excitation power for multiphoton endoscopic imaging compared to non-PM fibres

Summary

Introduction

M ULTIPHOTON microscopy [1] provides inherently optically sectioned images, enabling biochemical structure and activity to be studied in biological tissue [2]–[4], and is increasingly applied in vivo. To explore its potential for preclinical and clinical imaging, several groups are developing miniaturized instruments for multiphoton endomicroscopic imaging [5]–[14]. Most commonly these approaches are based on miniaturization of distal scanning and optical components integrated with a fibre-optic delivery system that can be implemented using double-clad large mode area photonic crystal fibre [15] or hollow-core photonic crystal fibre for minimal dispersion [16] with the double-cladding providing a high epi-detection.

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