English

This thesis is devoted, in the framework of cavity Quantum Electrodynamics, to the interaction of light with matter under an incoherent continuous pumping. As such, it describes physical systems like a quantum dot--that provides excitons (matter)--inside a semiconductor microcavity--that provides photons (light).

I consider two models to describe their interaction: the linear model (for bosonic excitons) and the Jaynes-Cummings model (for fermionic excitons). In the so-called strong coupling regime, photons and excitons interact strongly, loosing their identity and giving birth to new particles, called (0D) polaritons.

Polariton physics is greatly affected by decoherence. I add it to the theory through Lindblad terms in a master equation. The two main sources of decoherence in semiconductors are dissipation (losses of particles) and the off-resonant continuous wave scheme of excitation (continuous injection of particles). Although the effect of decay has been studied since the early days of cQED, the effect of incoherent pumping has been largely overlooked. I show how and when the interplay of pump and decay can hinder or favor the formation of polaritons.

The boson model is solved exactly and shows the qualitative and quantitative consequences that pumping bears in experiments, in particular in spectroscopic measurements of photoluminescence. The fermion problem is solved semi-analytically, and advocated as a laboratory tool to study the transition from quantum to classical regimes.

Observation of polaritons in the actual spectra of emission depends on the pumping and the nature of the excitons (bosonic or fermionic) in a crucial way that I unravel in this text. Other properties of these systems like first and second order correlations, one and two photon gain, lasing and entanglement are also discussed.