Imaging through a square multimode fiber by scanning focused spots with the memory effect

TL;DR

This paper demonstrates that the shift-shift memory effect in square multimode fibers enables imaging by scanning focused spots through wavefront shaping, eliminating the need for transmission matrix measurement.

Contribution

It shows how the memory effect can be used for fluorescence imaging through a multimode fiber without measuring the transmission matrix.

Findings

Memory effect observed in real space in square multimode fibers.

Fluorescence imaging achieved by wavefront shaping and scanning spots.

Imaging performed without transmission matrix measurement.

Abstract

The existence of a shift-shift memory effect, whereby any translation of the input field induces translations in the output field in four symmetrical directions, has been observed in square waveguides by correlation measurements. Here we demonstrate that this memory effect is also observed in real space and can be put to use for imaging purposes. First, a focus is created at the output of a square-core multimode fiber, by wavefront shaping based on feedback from a guide-star. Then, thanks to the memory effect, four symmetrical spots can be scanned at the fiber output by shifting the wavefront at the fiber input. We demonstrate that this property can be exploited to perform fluorescence imaging through the multimode fiber, without requiring the measurement of a transmission matrix.