Category Archives: Tutorial

Software Tutorial WP1

Layout: A Python module to generate macropixel patterns for SLMs and DMDs

In many wavefrontshaping experiments, such as for optimization experiments, like the seminal work by I. Vellkoop and A. Mosk, or for measuring the transmission matrix, one need to control the amplitude and/or the phase of the field on a given number of macorpixels (i.e. group of pixels). Using DMDs, amplitude and phase modulation can be acheived using the Lee hologram method and then sending the binary images to the device using the for ALP4lib in Python for Vialux DMDs. I release here a module written by myself and M. W. Matthes to easily and efficiently generate such patterns. The code can be found on my Github account here as well as an amplitude and phase modulation example: layout_amplitude_phase_modulation.ipynb.

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Tutorial WP1

Setting up a DMD/SLM: Aberration effects

Digital Micromirror Devices (DMDs) are amplitude only (binary) modulators, however, pretty much like liquid crystal modulators, they introduce some phase distortion. Practically, it means that if one illuminates the modulator with a plane wave, even when all the pixels are set to the same value, the wavefront shows phase distortions after reflection. That can be detrimental, especially when working in a plane conjugated with the Fourier plane of the DMD surface. Fortunately, using the Lee hologram method (or the superpixel method) one can achieve phase modulation. I present here how to use Lee holograms to characterize and compensate for aberrations when using a DMD. This approach can also be applied for compensating for aberration effects in other types of Spatial Light Modulators, such as liquid crystal ones.

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Software Tutorial WP2

pyMMF: A Python module for simulating multimode fibers

We relase a first version of our Python module based on the tutorial we posted to simulate the transmission matrix of straight and bent multimode fibers. The code is available on my GitHub account here. We also release two tutorials:

PyMMF: A benchmark with straight fibers

Bent fibers with pyMMF

 

 

Software Tutorial WP2

Simulation of multimode fiber modes: Straight and bent fibers

We present a two part tutorial on how to numerically estimate the modes of straight or bent multimode fibers of arbitrary radial index profile. It allows calculating the mode profiles, the propagation constants and estimating the transmission matrix of a segment of a multimode fiber with a reasonable computationnal complexity.

Part 1: Straight fibers

Part 2: Bent fibers

Tutorial WP1

Setting up a DMD: Diffraction effects [WP1]

DMDs are more complicated to use compared to liquid crystal SLMs due to the tilt of the pixels, making the system comparable to a blazed grating. The effect depends on the wavelength, the input angle and the pixel pitch and can significantly reduce the diffraction efficiency of the modulator. We present here a tutorial with simulations to understand and predict the diffraction effects when working with DMDs.

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