Stimulated emissions and quantum interference in potassium atom laser interaction

Abstract

The interaction of a laser with potassium atoms is investigated by monitoring the radiation of the 5P–4S transition under the two-photon 4S1/2 –6S1/2 excitation. For low number density and laser intensity the observed radiation is parametric axial or conical, depending on the laser detuning from the two-photon resonance, the number density and the laser intensity. With increasing laser intensities and number densities, an additional delayed component is observed corresponding to a two-step four-wave mixing with the participation of internally generated photons. A two-photon quantum interference effect is observed for the total (axial and conical) parametric four-wave mixing emission. A deviation from the proposed model under certain experimental parameters is attributed to a two-step four-wave mixing and the phase mismatch of the parametric processes.

Saturation and population transfer of a two-photon excited four-level potassium atom

“…This value is close to 0.11 (the ratio of the frequencies involved) as expected for a two-photon parametric process. This result agrees with the experimental results for sodium [1] and potassium atoms [6]. It was shown in [1,6] that the mechanism causing the linear response of the atomic medium is the destructive QI between the twophoton laser excitation and the excitation by the two photons 24 ω and 41 ω generated by the parametric process, which is 180 0 out of phase.…”

“…This result agrees with the experimental results for sodium [1] and potassium atoms [6]. It was shown in [1,6] that the mechanism causing the linear response of the atomic medium is the destructive QI between the twophoton laser excitation and the excitation by the two photons 24 ω and 41 ω generated by the parametric process, which is 180 0 out of phase. We should mention that by parametric process we mean either the simultaneous emission of two photons corresponding to the transitions 2 4 1 ↔ ↔ or the wave mixing of two laser photons with a photon which came from the SHRS process connecting the states 1 and 4 .…”

“…In order to compare the results of the simulation with relevant experimental results, we use the work of N. Merlemis et al [6]. In figure 8 a plot of ( ) …”

“…In our previous work, we have shown experimentally [6] and theoretically [8] in the case of potassium atom that even photon QI resulting from two different excitation paths to the 1/2 6S excited state, one by the two photon pumping laser and another by the generated fields, can lead to a linear dependence of the emitted radiation field on the excitation intensity. In this case, it was estimated that the ratio of the frequencies of the two generated photons is equal to the ratio of the corresponding intensities.…”

“…Specifically, in the case of the potassium atom, it was shown that the ratio int n of the peak intensities of the PFWM generated fields close to the [8]. It was also shown that for sodium [1,4] and potassium [6,8] atoms, the pumping laser intensity and the atom number density are crucial factors that determine whether the destructive QI effect is insignificant (nonlinear region) or dominant (linear region). In order to elucidate the relative importance and complicated interplay of the various parameters of the driving laser and the atomic system, we have set out to model the dynamics of the laser-driven four-level system.…”