Selective femtosecond laser ablation via two-photon fluorescence imaging through a multimode fiber.

Eirini Kakkava,Demetri Psaltis,Marilisa Romito,Christophe Moser,Konstantina M Stankovic,Donald B Conkey,Damien Loterie

doi:10.1364/boe.10.000423

Abstract

We demonstrate the ability of a multimode fiber probe to provide two-photon fluorescence (TPF) imaging feedback that guides the femtosecond laser ablation (FLA) in biological samples for highly selective modifications. We implement the system through the propagation of high power femtosecond pulses through a graded-index (GRIN) multimode fiber and we investigate the limitations posed by the high laser peak intensities required for laser ablation. We demonstrate that the GRIN fiber probe can deliver laser intensities up to 1.5x1013 W/cm2, sufficient for the ablation of a wide range of materials, including biological samples. Wavefront shaping through an ultrathin probe of around 400 μm in diameter is used for diffraction limited focusing and digital scanning of the focus spot. Selective FLA of cochlear hair cells is performed based on the TPF images obtained through the same multimode fiber probe.

Highlights

Optical fibers are important clinical tools because they allow access to confined places in a minimally invasive way
We report for the first time femtosecond laser ablation (FLA) through multimode fibers combined with twophoton fluorescence (TPF) imaging through the same multimode fiber
We demonstrate for the first time a multimode fiber (MMF) fiber probe that is able to perform FLA with high selectivity based on the TPF image of the sample, which is obtained through the same probe

Summary

Introduction

Optical fibers are important clinical tools because they allow access to confined places in a minimally invasive way. Further increase in the input pulse energy is limited by the nonlinearities and damage that can arise in the optics and scanning mechanism at the distal end that are necessary for focusing the light. Most commercially available tools use either single mode fibers (SMFs) combined with optical components to focus the light at the distal side and scanning mechanisms to steer the light around the region of interest or fiber bundles that result in pixelated images [1,17,19,20,21,22]. We use two GRIN fibers of 200 μm and 400 μm diameter core size to test their performance in delivering a high peak intensity femtosecond focus spot for laser ablation applications in biological samples. By developing a technique with imaging modalities integrated with selective laser ablation capabilities, we provide a minimally invasive system for both cellular level investigation of distinct target areas and for cell manipulation

Optical setup

Cochlear sample preparation

High peak intensity delivery through GRIN fibers

Findings

Conclusions