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Guillaume Graciani, IP Paris Thesis Award

par Anne-Marie - publié le

Guillaume Graciani did his thesis from September 2017 to October 2020 under the joint supervision of François Amblard at UNIST (Ulsan, South Korea), and Marcel Filoche at École polytechnique. He was awarded the IP Paris Best Thesis Award Runner-up.

His doctoral thesis, entitled “Three-dimensional stochastic interferometry : theory and applications to high-sensitivity optical metrology and light scattering amplification”, introduced a new principle of “stochastic” interferometry enabling to detect with an unparalleled precision (sub-picometric) geometric modifications (and therefore internal dynamics) within a cavity.

Guillaume Graciani began his thesis by developing an optical cavity of very high level of reflectivity (albedo), allowing for the first time the realization of a three-dimensional “Berry field”, a theoretical concept initially proposed by Michael Berry and consisting of a coherent stochastic electromagnetic field with a very high level of symmetry. The coherence of the field and the albedo achieved thus open the possibility of an interferometric measurement with a "very large number of arms" at any point inside the cavity. Guillaume then exploited this electromagnetic field to demonstrate the ability of this interferometric device to measure picometric variations in the internal geometry of the cavity (patent pending).

This record albedo was immediately exploited to efficiently collect the light coming from very low intensity volume sources placed in the cavity. Guillaume thus described theoretically and experimentally measured the noise of the system, showing that the optimum sensitivity (with an EMCCD camera) made it possible to detect 110 photons/s per liter. This performance was applied to the detection of very low emissions : to begin, the production of light by yeasts and, for the first time, the observation of luminescence produced by a very simple chemical reaction, the disproportionation of H_2 O_2 in water.