Side bands in collective resonance fluorescence

The fluorescence spectrum of a system of strongly driven atoms, contained in a region that is small compared with the wavelength, is calculated using a screened interaction model. Coulomb dipole–dipole interaction is neglected, but a Markov approximation is not made. The side bands at ω′ = ω ± Ω and ω ± 2Ω are investigated in detail (ω′(ω) is the emitted photon (pump field) frequency; Ω is the Rabi frequency). The intensity and line width of the side bands at ω ± 2Ω is reduced owing to S breaking in our model. Non-Markovian corrections split the side band at ω ± Ω.