ERRATUM: Diffraction Effects in DMDs

I made a big mistake in the calculation of the DMD diffraction effects, it affects the following posts:

• A practical guide to Digital Micro-mirror Devices (DMDs) for wavefront shaping, and also the corresponding paper,
• Setting up a DMD: Diffraction effects,
• The online tool.

These will be edited shortly to reflect the corrections, as well as the paper A practical guide to digital micro-mirror devices (DMDs) for wavefront shaping (DOI, Arxiv) that will be retracted and resubmitted.

Long story short, the grating equation was wrong. It should not affect too much the results for low angles, but given the fact that the angles of each micro-mirror is already 12 degrees, it is not negligible at all.

The correct grating equation should be:

\[
  \text{sin}(2\theta_B-\alpha') + \text{sin}(\alpha')
  = 2 \,\text{sin}(\theta_B)  \,\text{cos}(\theta_B-\alpha')
  = p\frac{\sqrt{2}\lambda}{d} \, ,
\]

with the same notations as in the tutorial, so the blazed number then reads:

\[
  \mu =
  \left| 4 \frac{d}{\lambda\sqrt{2}}
  \left[
    \text{sin}(\theta')\text{cos}(\theta'-\alpha')
    \right]
  \mod{2} -1
  \right| \, .
\]

Big thanks to L. Malosse and @NiuYihan1999 for pointing out this error.

Harnessing disorder and symmetries in multimode fibers

Sébastien M. Popoff
IESC Cargèse, France
April 2024

We present how to study light propagation in multimode fibers using transmission matrix measurements and apply it to understand the effect disorder and its impact on the so-called rotational memory effect. This talk is part of the Wave Propagation and Control in Complex Media 2024 workshop (15-19 April 2024, Cargèse, France)

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.