Optical transitions in a two-level system in the presence of a strong low-frequency field

G. I. Toptygina, Evald E. Fradkin

В. Г. Коломиец

Lung Ko, Michael W. Noel, Jonathan M. Lambert +1 more

We have investigated multiphoton transitions driven by two harmonically related microwave fields in a two-level system. We observed pronounced dependence of the Rabi frequency on the amplitudes and relative phase of the fields in the low field limit and found that the Rabi frequency of the combined fields was given by the phasor sum of the Rabi frequencies of the individual fields. For strong fields, each individual Rabi frequency is modified by the presence of the other field and this intuitive phasor addition is no longer valid.

Constantine Mavroyannis, M. P. Sharma

We consider the possible physical processes that may arise in a three-level atom when only two of its levels interact with a strong electromagnetic field and when the atomic transition frequency is nearly equal to once and twice the frequency of the laser field, respectively. There have been found pronounced cooperative effects in the spectrum of the two-level system, which is in resonance with the laser field, arising from the presence of the third level. The excitation spectra describing the transitions from the first excited state into the second excited state and from that to the ground state consist, apart from the two central peaks, of two pairs of sidebands which are induced by the laser field of the neighbouring system. Detailed expressions of the spectral functions for the physical processes of one- and two-photon resonance fluorescence have been derived and discussed in the limit of high photon densities. The excitation spectrum of the low frequency modes has been considered and discussed in detail. It is found that quantum beats in spontaneous emission may appear in the spectra of the one- and two-photon resonance fluorescence arising from the interference between the two atomic transition frequencies and the frequency of the laser field. The importance of the low frequency modes that occur in the processes in question has been pointed out.

M. Kira, Stephan W. Koch

Nikolai B. Delone, В. П. Крайнов, V. A. Khodovoǐ