Quantum emission between the weak and strong coupling regimes

The emission properties of single-photon sources (a) attached to photonic nanostructures in the weak and strong coupling regimes have been intensively studied. However, often new opportunities arise in physical systems that operate at intermediate regimes between the more studied extreme cases. Here, we analyze the emission properties of a two-level system coupled to a two-mode cavity. Our analysis demonstrates that there is an intermediate regime, between the weak and strong coupling regimes, which offers an additional degree of freedom in controlling the bandwidth of a single-photon source, even when it is incoherently excited. In turn, this degree of freedom can be harnessed to decouple efficiency and bandwidth, thus bringing additional flexibility in the design of efficient photon sources with (b) controllable bandwidth.