Final Report Summary - BIGEXPO (Bilayer Graphene Exciton Polariton) The BiGExPo project aims to study the strong coupling of gapped graphene bilayers to a microcavity photonic field.Given the very large excitonic dipole moment of such a material, recently predicted by ab-initio calculations, this system could potentially open new frontiers of research in the domain of solid-state cavity quantum electrodynamics, both by allowing us to observe a novel, strongly correlated light-matter coupling regime, and by empowering a novel generation of terahertz and mid-infrared super-efficient optoelectronic devices.During the first year of the BiGExPo project, I investigated the physics of a graphene bilayer sheet nonperturbatively coupled withthe photonic field of a cavity. The investigation proceeded in two complementary directions. On one side, I studied what happens when adipole layer (modelling the graphene sheet) is nonperturbatively coupled to the electromagnetic field. This led to two important publications, inwhich I showed that in this extreme regime the Purcell effect breaks down (S. De Liberato, PRL 112, 016401 (2014)) and that usually safeapproximations used to study photonic emission have to be modified (S. De Liberato, PRA 89, 017801 (2014)).On the other side, I started to develop a microscopic theory describing the coupling between excitons in graphene bilayers andphotons. This is an ongoing effort that should give the first results in the next few months. Once the microscopic coupling theory will be ready, I will thus be able to give a comprehensive description of the physics of light-matter coupling in bilayer graphene, accounting for new fascinating physical effects due to the nonperturbative nature of the coupling.N.B. The project ended at the end of the first year, because I had to start working on a different project, after having been awarded a prestigious 5-years Royal Society University Fellowship. For this reason the final report summary is a copy of the periodic report summary, having them been written at the same time.