MASTER Internship
The study of light propagation in disordered materials - such as biological tissues, layers of paint, fog or multimode fibers – has strongly attracted the attention of the optics community during the past decades. When light propagates in such complex systems, light is scattered by the heterogeneities of the medium and all the information carried by light seems to be lost. For example, it is impossible to see through a dense fog because light is multiply scattered by the water droplets. When a coherent light beam propagates through such a medium, it yields a complex, seemingly random interference pattern, a so-called speckle pattern.
However, it has been recently demonstrated that the distortions induced by scattering can be pre-compensated by shaping the optical wavefront before propagation in the complex medium. For example, light can be focused through an opaque layer of paint and objects hidden behind scattering media can be imaged. Recently, these novel techniques have been used to control light propagation through multimode fibers. Similarly to the case of a scattering medium, light propagates in a multimode fiber following different optical paths. The propagation modes of the fiber then accumulate different phase retardations, and recombine in an uncontrolled way, yielding a speckle pattern at the output of the fiber. By pre-compensating this mixing process with light shaping techniques, such systems are expected to play an important role for imaging or communication purposes.
The internship project we propose aims at studying and controlling light propagation in multimode fibers in a specific configuration, called the "fiber loop" configuration. In this configuration, light propagates through a bended multimode fiber where a part of the output light is directly re-injected in its input. Light collected at the output is then composed of photons that has performed different numbers of fiber loops.
The main objectives on the internship is to develop the experimental setup and use light shaping techniques to control light propagation in the system. The student will be working on experimental optical setups. Programming skills and a strong background in experimental optics are required. This project has been carefully designed to enable the student to progress step-by-step with some intermediate goals to reach.
Place : Institut Fresnel, MOSAIC group
Time : Flexible duration of the internship (> 3 months) & flexible period
Supervisor : thomas.chaigne@fresnel.fr
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