Ultra-thin rigid endoscope: Two-photon imaging through a graded-index multi-mode fiber

TL;DR

This paper introduces an ultra-thin, 125-micron diameter rigid endoscope using graded-index multi-mode fiber, enabling two-photon fluorescence imaging for biological samples with high spatial resolution.

Contribution

It demonstrates for the first time the feasibility of two-photon imaging through an ultra-thin graded-index multi-mode fiber endoscope.

Findings

Successful acquisition of optically sectioned two-photon fluorescence images

Miniaturization of endoscope to 125 microns diameter

Validation on three-dimensional biological samples

Abstract

Rigid endoscopes like graded-index (GRIN) lenses are known tools in biological imaging, but it is conceptually difficult to miniaturize them. In this letter, we demonstrate an ultra-thin rigid endoscope with a diameter of only 125 microns. In addition, we identify a domain where two-photon endoscopic imaging with fs-pulse excitation is possible. We validate the ultra-thin rigid endoscope consisting of a few cm of graded-index multi-mode fiber by using it to acquire optically sectioned two-photon fluorescence endoscopic images of three-dimensional samples.