Thesis defense of Aurelian Loirette--Pelous

Thesis defense of Aurelian Loirette--Pelous, PhD student in the Nanophotonics group of the Laboratoire Charles Fabry, on 05 June 2023 at 2pm in the Auditorium of the Institut d'Optique Graduate School in Palaiseau, on the topic: "Theoretical study of light emission by an assembly of emitters thermalised in a resonator".

Abstract: "Controlling the properties of light emission (spontaneous emission rate, spectrum, directivity, polarisation, etc.) is at the heart of many current applications. One remarkably effective approach is to use a resonator, such as a cavity or a nanoantenna, to modify the emission process by one or more emitters. In particular, many resonant devices based on solid-state emitters have been studied. However, the theoretical modelling of these devices is more complex than for those based on a single emitter, and has been little explored.  In this thesis, we develop and test new theories for the study of light emission from solid-state emitters via a resonator, in the particular case where the emitters are locally thermalized. In this hypothesis, the quantities characterising the emission are simply the absorptivity of the system, the temperature of the carriers and their quasi-Fermi levels. It has recently been suggested that an extension of Kirchhoff's law to locally thermalized systems enables the properties of the emission to be predicted quantitatively. This modelling tool is central to this thesis. Four problems are addressed: (i) Metasurface control of spontaneous emission from an ensemble of colloidal quantum dots is studied. An excellent agreement between simulations with the generalised Kirchhoff law and existing experimental data is presented, demonstrating the validity of this new theoretical tool. (ii) An in-depth study of the generalised Kirchhoff law is carried out, highlighting its validity in the laser regime. (iii) The phenomenon of photoluminescence by a metal pumped by a laser is studied. Under continuous pumping, approximations are used to establish a generalised Kirchhoff law, even though the emitters are not thermalised. Good agreement between this model and experimental data is found. (iv) The phenomenon of Bose-Einstein condensation of photons is studied, and in particular its link with the laser regime of thermalized emitters in a resonator. An out-of-equilibrium generalisation of the Bose-Einstein distribution is introduced, making it possible to link these two regimes and to rethink the laser regime of a multimode resonator".