All-optical image transportation through a multimode fibre using a miniaturized diffractive neural network on the distal facet

Abstract

The direct optical transportation of images through multimode fibres (MMFs) is highly sought after in compact photonic systems for MMF-based optical information processing. However, MMFs are highly scattering media, thus degrading information transmitted through them. Existing approaches utilize artificial neural networks or spatial light modulators to reconstruct images scrambled after propagation through the fibre. Despite these advances, achieving direct optical image transportation through MMFs using integrated optical elements with micrometre-scale footprints remains challenging. Here we develop a miniaturized diffractive neural network (DN₂s) integrated on the distal facet of a MMF for the direct all-optical image transportation through the fibre. The DN₂s has a footprint of 150 μm by 150 μm and is fabricated on the facet of a 0.35-m-long MMF using three-dimensional two-photon nanolithography. The fibre-integrated DN₂s enables single-shot optical transportation of images with flat phases in real time for a constant configuration of the MMF. The system achieves a minimum image reconstruction feature size of approximately 4.90 μm over a field of view 65 μm by 65 μm when imaging handwritten digits. Transfer learning is also demonstrated by the direct optical transportation of HeLa cell images projected by spatial light modulators, which were not part of the training dataset. The concept and implementation pave the way to the integration of miniaturized DN₂s with MMFs for compact photonic systems with unprecedented functionalities.