emittercavity

An emitter–cavity system, or emitter in a cavity, refers to a quantum emitter such as a two‑level atom, a quantum dot, or a color center placed inside an optical or microwave cavity whose resonant mode strongly interacts with the emitter’s transition. The cavity provides a discrete electromagnetic mode with resonance ωc, a quality factor Q, and a mode volume V, shaping the density of optical states available to the emitter.

In cavity quantum electrodynamics, the interaction is described by the Jaynes–Cummings model with coupling strength g. The decay rates are the emitter’s spontaneous emission rate γ and the cavity field decay rate κ. In the weak coupling regime, g ≪ {κ, γ}, emission into the cavity is enhanced by the Purcell effect, with a factor Fp ≈ (4g^2)/(κγ) ≈ (3/4π^2)(λ/n)^3(Q/V). This channels more photons into the cavity mode, increasing brightness and directionality and enabling efficient photon extraction. In the strong coupling regime, g > {κ, γ}, coherent energy exchange produces vacuum Rabi splitting and mixed light–matter states (polaritons).

Common platforms include semiconductor microcavities with embedded quantum dots, photonic crystal nanocavities, micropillar cavities, ring resonators, and whispering-gallery modes; implementations also exist with atoms in optical resonators, color centers in diamond, and superconducting qubits in microwave cavities.

Applications span deterministic single-photon sources, quantum information processing, indistinguishable photons, and quantum networks. The emitter–cavity framework is described by the Jaynes–Cummings Hamiltonian and analyzed with master equations and input–output theory, while practical considerations include dephasing, spectral diffusion, and fabrication losses.