Controlling a Spatial Light Modulator remotely using a Raspberry Pi

Standard phase spatial light modulators (SLMs) have the advantage of being controlled as a secondary display. It saves money on dedicated control interfaces and simplifies the usage. However, when trying to control an experiment remotely, which is especially needed these days, It adds some complexity when using remote desktop software or ssh. I will detail here how to use a Raspberry Pi to control an SLM and send images from a computer on the same local network. The computer that controls the experiment can now easily be controlled from the comfort of your home.

Fast numerical estimations of axisymmetric multimode fibers modes

Estimating the propagation constants and the transverse mode profiles of multimode fibers is not as easy as it sounds. In our recent work we highlighted here, we needed to estimate the mode profiles for a standard graded-index fiber. It turned out that many standard approximations done in the literature to estimate the propagation constants do not give results accurate enough for the mode profile. The general approach we introduced in a previous tutorial to numerically find the fiber modes for any index profile using a 2D scalar finite differences approach is still valid. However, to provide accurate results, it needs a fine discretization of the space that leads to important memory and computational time requirements when the fiber core increases. If we consider an axisymmetric fiber, we can obtain a 1D formulation of the problem, that is unfortunately unstable under naive finite differences approaches. We detail here a stable formulation that leads to accurate and fast estimations of the mode profiles.

Easy characterization of SLMs' phase deformation

[D. Marco et al., Opt. Lett., 45 (2020)]

Technical papers are important for the scientific community, it helps in particular to reproduce experimental setups. They are unfortunately not valued enough by scientific journals. I want today to highlight such a paper. Liquid crystals phase modulators - and indeed any kind of spatial light modulator (SLM) - are not free of imperfections. One effect that appears is a phase distortion of the reflected field due to spatial non-uniformities that occur during the fabrications. In practice, if you illuminate an SLM with a plane wave and you display a uniform mask, one does not end up with a plane wave, but an aberrated wavefront. In the present paper, the authors use a quite easy to implement technique to retrieve the phase distortion introduced by the SLM.

Making useless (but beautiful) gifs with fiber modes

Social media like (too) short content like pictures or quotes, but above all, people love gifs (probably way too much). Publish a link to a few pages long post you wrote about a paper, a physical concept, or a piece of code, and a few people will like your tweet/post. Publish a gif, and the number of people you will reach will increase dramatically. Is it a good thing? Well, that depends on what you do with it. I try to use gifs to draw attention to more in-depth content that I hope some people will read. Let's make one together.