Wavefront shaping techniques in complex media
- Details
- Category: Multimode fibers
- Published on Thursday, 13 December 2018 10:29
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[tutorial] Numerical Estimation of Multimode Fiber Modes and Propagation Constants:
Part 1: Straight Fibers
Under 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 presence of bending. I released a beta version of the Python module pyMMF based on such 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 spare matrix representing the equation on the discretized space.
- Details
- Category: Spatial Lights Modulators (SLMs)
- Published on Friday, 21 September 2018 09:18
How to calibrate linearly aligned nematic liquid crystal based SLMs [tutorial]
We published previously a tutorial presenting a technique to calibrate spatial light modulators (SLMs). The approach was based on measuring the interference between two paths that have been reflected off two different regions of the SLM. This technique is always valid but requires aligning a mask, using a lens and capturing and treating images of interference patterns. Nowadays, most phase only SLMs based on liquid crystals use linearly aligned nematic crystals. Unlike twisted nematic liquid crystals, they allow phase only modulation on one polarization while not affecting the orthogonal polarization. This feature can be used to simplify the calibration setup to characterize the SLM with a common path interferometer, not requiring a precise alignment [1]. Furthermore, it only needs a photo-detector, compared to a digital camera in the previously presented approach. This is convenient to measure the inevitable phase fluctuations of an SLM, usually around a 100 to 400 Hz frequency. In this document, we briefly describe the principle of the characterization scheme as presented in [2] and show typical results of the calibration and the phase fluctuations.
Written by Paul Balondrade and Sébastien M. Popoff
- Details
- Category: Postdoc offers
- Published on Friday, 14 September 2018 09:53
Postdoctoral Research Associate/Fellow
Spatiotemporal properties of light in multimode optical fibre
School of Information Technology and Electrical Engineering (ITEE), The University of Queensland, Brisbane, Australia.
We seek applications from suitably qualified candidates who will focus on the development of optical systems for the measurement and manipulation of the spatial, spectral and temporal properties of light in multimode optical fibre. The position is funded under an Australian Research Council (ARC), Discovery Project in collaboration with the University of Southampton and industrial partners Nokia (Bell Labs, US) and Finisar Australia.
Examples of previous work in this area available here : https://www.youtube.com/user/joelacarpenter
Duration: 2-3 years
More information: here
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- Category: Events
- Published on Tuesday, 10 April 2018 08:17
OIP'21 : Optics for information processing in the 21th century
May 23th - May 26th 2018
Villa Finaly
Florence, Italy
Hosted by: Sylvain Gigan (LKB, Sorbonne Université Paris, Paris), Rafael Piestun (University of Colorado, Boulder, USA)
Link: here
- Details
- Category: Events
- Published on Monday, 26 February 2018 11:02
Complex 2018 Summer school
Transport, Mesoscopy and Imaging in Complex Media
May 28th - July 1st 2018
The Institute of Scientific Studies
Cargèse, Corsica, France
Hosted by: Nicolas Cherroret (Laboratoire Kastler Brossel, Paris), Alexandre Aubry (Institut Langevin, Paris)
Link: here
- Details
- Category: PhD offers
- Published on Thursday, 31 August 2017 09:13
Complex Photonics Lab is recruiting MSc, PhD and Postdocs
Racah Institute of Physics, The Hebrew University of Jerusalem, Israel
We are looking for excellent and highly motivated students and postdocs. Research projects for 3rd and 2nd year BSc students are also available.
