Two Dipole-Dipole Interacting Emitters in a Moderately Strong Laser Field
摘要
The cooperative resonance fluorescence spectrum for a non-resonantly laser-pumped pair of dipole-dipole coupled two-level radiators is explored. The dipoles are confined in a small volume within the Dicke limit, i.e., when the inter-emitter distance is much smaller than the emission wavelengths. Also, a non-trivial detuning between the laser and emitter transition frequencies is considered. Several approximations have been used, including the electric dipole approximation, the rotating wave approximation, and a rotating frame of reference taken at the laser’s pumping frequency. The emitters are driven by a moderately strong coherent electromagnetic field, and the dipole-dipole coupling strength—having the dimension of frequency—significantly exceeds the collective decay rate while remaining much smaller than the doubled Rabi frequency. This frequency, manifested by the system is, in turn, much smaller than the emitter transition frequencies. We obtained the characteristic two-qubit Mollow spectrum consisting of the elastic part and, respectively, the spontaneous resonance fluorescence part of the spectrum, i.e., the central, as well as the left and the right spectral bands. The study discusses the vanishing elastic part of the spectrum and the dressed states dipole-dipole interaction. It shows the proper analytic ratio between the non-zero detuning of the system and the doubled Rabi frequency to achieve the ensuing result.