Master intership + PhD at the Langevin Institute

Invariant Properties in Multimode Fibers for Imaging Applications

We are recruiting a master student with the possibility to continue during a Ph.D (funded) to work on the study of light propagation in multimode fibers using wavefront shaping and numerical reconstruction algorithms (phase retrieval, deep learning). Join un in Paris!

Keywords: waveftont shaping, mutlimode fibers, mesoscopic physics, phase retrieval, deep learning

See our recent publication: 

• [Learning and avoiding disorder in multimode fibers, Phys. Rev. X, 2021]
• [Tailoring the Rotational Memory Effect in Multimode Fibers, arxiv, 2023]

TL;DR:
We will play with deep learning frameworks to develop new approaches for calibration-less imaging through multimode fibers based on the study of invariant properties in multimode fibers.

Contact: Sébastien Popoff - sebastien.popoff(at)espci.fr

More information here.

All-fiber Control of Entanglement:
Recovering Correlations via Mechanical Perturbations in a Multimode Fiber

In quantum optical communications, single photons can be used as a unit of quantum information. However, one can supercharge their capacity to carry information by encoding high-dimensional quantum dits, or qdits, into their transverse shape. They allow having more than two levels per unit of information as it is the case for bits. In fiber optical communications, it requires using multimode fibers to harness the spatial degrees of freedom to encode the qduts. However, when propagating through a real-life multimode fiber, the transverse shape of the photons gets scrambled because of mode mixing and modal interference. This scrambling of transverse shape is typically rectified using free-space spatial light modulators. But, this remedy prevents us from achieving a truly resilient all-fiber operation and requires a careful alignment and lab-graded stability hindering real-life implementation. In [R. Shekel et al., Arxiv 2306.02288 (2023)], the authors introduce an all-fiber method for controlling the shape of single photons and spatial correlations between entangled photon pairs. They do so by implementing carefully controlled mechanical perturbations to the fiber.

Spatiotemporal control of light

Joel A. Carpenter
May 2021

This tutorial investigates various techniques for spatial and/or temporal optical beam manipulation.

Learning and Avoiding Disorder in Multimode Fibers

Sébastien M. Popoff
July 2021

In this work, we demonstrate the existence of a set of spatial channels in multimode fibers that are robust to strong local perturbations. We show that, even for a high level of disorder, light propagation can be characterized by just a few key properties.

Related article: doi.org/10.1103/PhysRevX.11.021060