Sidebands shifts and induced sidebands in rf-dressed Rydberg systems

The effect of an ac modulation on a 2-level or 3-level system is studied theoretically. The absorption spectrum is calculated by solving the optical Bloch equations and is interpreted by reference to the Floquet quasienergy spectrum. The dependence of the absorption sidebands on the intensity of the coupling laser field in Rydberg systems submitted to a radio-frequency (rf) field is analysed in detail. It is shown that for sufficiently strong coupling fields additional sidebands appear in the probe absorption spectrum in ladder 3-level systems. These additional sidebands are induced by the coupling of the intermediate state to the Floquet manifold spawned by the upper state under rf modulation.