Rabi sideband emission from transient excitation gratings in cross-beam filament channels in a dense gas*

Femtosecond laser filamentation in dense gases gives rise to extensive generation of excited atoms or molecules. We consider transient excitation and ionization gratings formed at the crossing of two laser beams and effectively controlled by the temporal shape of the replicated laser pulse. A probe picosecond laser pulse, when incident normally on thus produced transient grating, couples with pairs of states in the excited state manifold, resulting in Rabi oscillations and Rabi sidebands emission at frequencies red- and blue-shifted about the carrier frequency of the probe beam. The emitted radiation is involved in spatial and spectral interference and produces complicated interference patterns available for remote detection. These patterns are sensitive to the excitation grating properties, such as the bean crossing angle, the phase shift between the two grating-producing pulses, the gas pressure, and the orientation of the grating with respect to the probe beam. Addressing the case of high-pressure argon gas, we investigate quantitatively modifications of the Rabi sideband interference patterns controlled by manipulation of these parameters and reflecting the state of the gas excitation in the transient filament-wake gratings.