Two-photon imaging through a multimode fiber

TL;DR

This paper demonstrates high-resolution 3D two-photon fluorescence imaging through a multimode fiber using digital phase conjugation, achieving micrometer-scale resolution and depth sectioning in a compact setup.

Contribution

It introduces a novel method for 3D two-photon imaging through a multimode fiber with digital phase conjugation, enabling high-resolution imaging in a compact form.

Findings

Achieved 1 micrometer lateral resolution and 15 micrometer axial resolution.

Demonstrated depth sectioning in a 3D sample with fluorescent beads.

First high-resolution 3D two-photon imaging through a multimode fiber.

Abstract

In this work we demonstrate 3D imaging using two-photon excitation through a 20 cm long multimode optical fiber (MMF) of 350 micrometers diameter. The imaging principle is similar to single photon fluorescence through a MMF, except that a focused femtosecond pulse is delivered and scanned over the sample. In our approach, focusing and scanning through the fiber is accomplished by digital phase conjugation using mode selection by time gating with an ultra-fast reference pulse. The excited two-photon emission is collected through the same fiber. We demonstrate depth sectioning by scanning the focused pulse in a 3D volume over a sample consisting of fluorescent beads suspended in a polymer. The achieved resolution is 1 micrometer laterally and 15 micrometers axially. Scanning is performed over an 80x80 micrometers field of view. To our knowledge, this is the first demonstration of high-resolution three-dimensional imaging using two-photon fluorescence through a multimode fiber.