Created by sebastien.popoff on 16/09/2020
## Postdoctoral position: Matrix approach for resonant multiple scattering of light (theory)## Langevin Institute, ParisWe propose a 2 years postdoctoral position in the |

Created by sebastien.popoff on 23/06/2020
## DMD diffraction toolI presented in this tutorial the diffraction effects occurring in a DMD setup. It corresponds to a blazed grating effect and depends on the wavelength \(\lambda\), the pixel pitch \(d\), the incident angle \(\alpha\), and the angle of the micro-mirrors \(\theta\). Here is a simple app (see source code on Github) to calculate the criterion for optimal diffraction efficiency and the aspect of the diffraction pattern in the far-field when illuminating the DMD with a plane wave of incident angle \(\alpha\) with respect to the normal of the surface. |

Created by sebastien.popoff on 22/05/2019
## Semidefinite Programming for Intensity Only Estimation of the Transmission Matrix
The possibility of measuring the transmission matrix using intensity only measurements is a much sought-after feature as it allows us not to rely on interferometry. Interferometry usually requires laboratory-grade stability difficult to obtain for real-world applications. Typically, we want to be able to retrieve the transmission matrix from a set of pairs composed of input masks and output intensity patterns. However, this problem, which corresponds to a phase-retrieval problem, is not convex, hence difficult to solve using standard techniques. The idea proposed in [I. Waldspurger |

Created by sebastien.popoff on 13/12/2018
## Numerical Estimation of Multimode Fiber Modes and Propagation Constants:## Part 1: Straight FibersUnder the weakly guided approximation, analytical solutions for the mode profiles of step-index (SI) and graded-index (GRIN) multimode fibers (MMF) can be found [1]. It also gives a semi-analytical solution for the dispersion relation in SI MMFs, and, by adding stronger approximations, an analytical solution for the parabolic profile GRIN MMFs [2] (note that those approximations do fail for lower order modes). An arbitrary index profile requires numerical simulations to estimate the mode profiles and the corresponding propagation constants of the modes. I present in this tutorial how to numerically estimate the scalar solution for the profiles and propagation constants of guides modes in multimode circular waveguide with arbitrary index profile and in the presence of bending. I released a beta version of the Python module pyMMF based on such an approach [3]. It relies on expressing the transverse Helmholtz equation as an eigenvalue problem. Solutions are found by finding the eigenvectors of a large but sparse matrix representing the equation on the discretized space. |