Vladimir SEMENOV : "All-optical spatial light modulators for the design [...]

PhD works of SEMENOV : "All-optical spatial light modulators for the design of new processors based on complex dynamic systems"

Abstract : In this thesis, we show that coherent and incoherent illumination of an OASLM subjected to optical feedback allows the implementation of a wide range of coupled nonlinear oscillator networks with very diverse but adjustable bifurcation scenarios. We analytically derive the conditions for implementing stable state bifurcations, either fork, transcritical or node-col, without modifying the studied systems and simply by tuning the relative optical intensities of our two-color illumination at two laser wavelengths.

Spatially extended bistable systems can be structured into spatial domains comprising either equilibrium state, such that the fronts separating the domains move and either state asymptotically invades all available space in time. Using a spatial OASLM model, we demonstrate that fork and node-neck bifurcations control the speed and direction of wavefront propagation in spatially extended bistable systems. In addition, fork bifurcation conditions allow us to control the symmetry of bistable systems and we use them to emulate spin networks based on the dynamics of the autonomous OASLM. In particular, by exploiting the experimental symmetries, we simplify the equations of the corresponding system and demonstrate that such an optical system using an OASLM allows to realize an Ising machine. Using experimental characterizations of a particular OASLM based on nematic liquid crystals and amorphous nanoscale arsenic trisulfide (a-As2S3) chalcogenide glassy films, we find that such a system is capable of implementing up to 10000 nodes per mm2 requiring illumination intensities of only 10 nW/mm2 at 450 nm. With such characteristics, OASLMs appear as very promising candidates for the implementation of autonomous photonic neural networks realizing new optical computing architectures with very low energy consumption.

Jury Composition  :

Daniel BRUNNER, Researcher, Université Bourgogne Franche-Comté, PhD Director

Kathy LÜDGE, Professor, Université technique d'Ilmenau, Reporter

Tomasz KAPITANIAK, Professor, Université de technologie de Lodz, Reporter

Laurent LARGER, Professor, Université Bourgogne Franche-Comté, PhD Co-director

Serhiy YANCHUK, Researcher,Potsdam Institute for Climate Impact Research, Reviewer

Maxime JACQUOT, Professor, Université Bourgogne Franche-Comté, Reviewer

Localization : Amphithéâtre J.J Gagnepain, Bâtiment TEMIS, 15B, Avenue des Montboucons 25000 Besançon