Absorption of probing radiation by a two-level system in a noise pumping field

Gennady M. Krochik

А. И. Пархоменко, Anatolii M. Shalagin

Amplification of probe radiation by an inversionless two-level system in the 'red' wing of its spectral line is studied theoretically during the resonance absorption of intense cw laser radiation. The effect is caused by the inequality of the spectral densities of the Einstein coefficients for absorption and stimulated emission outside the absorption line under conditions when homogeneous broadening, due to the interaction of particles with the buffer gas, significantly exceeds the natural broadening (at high pressures of the buffer gas). It is found that the larger the inversionless gain, the higher the buffer gas pressure and the pump radiation intensity. It is established that at high enough pump intensity, the probe field is amplified along the entire region of the 'red' wing of the line (at any negative detunings of the probe field frequency).

Guiyin Zhang, Shicheng Hu, Qiyong Tao +3 more

Arindam Ghosh, Khairul Islam, Suman Mondal +3 more

Abstract Coherent probe field (L A ) propagation through an eight-level inverted Y-type atomic system, in the presence of two additional coherent radiation fields termed the field L C (control or pump field) and the field L B (repump field), is investigated by using the parameters of 87 Rb 5 S 1 / 2 → 5 P 3 / 2 → 7 S 1 / 2 transitions. The system has two ground energy levels, four intermediate energy levels, and two uppermost energy levels. A theoretical model based on the density matrix method is used for numerical simulation of the probe response under different conditions. Simulated probe absorption spectra under a Doppler-free condition as well as under thermal averaging exhibit electromagnetically induced transparency (EIT). The position and line shape of this EIT profile change with different detunings of the control and repump fields. When the three coherent fields share a common level, a funnel-like EIT window appears in the simulated probe absorption curve. Velocity selective optically pumped absorption peaks are seen in the simulated probe response at room temperature.

Bibhas Kumar Dutta, P.K. Mahapatra

We have analyzed the properties of weak probe absorption in a closed four-level Y -type system driven by a coherent driving field. The system with two nearly degenerate uppermost levels interacting with the same modes of the vacuum radiation field exhibits the interference effect between the spontaneous decay channels. The phenomenon of this quantum interference can significantly change the absorptive response of the weak probe field. On varying the amplitude of the resonant driving field, in the absence of incoherent pumping in the upper transitions the system can display probe transparency as well as enhanced absorption peak under the condition of resonant detuning of the probe field. With the application of incoherent pumping to the system the phenomenon of symmetric light amplification with two distinct gain peaks one each at the positions of Autler–Townes resonances can be achieved in the presence of the decay-interference effect. We have also shown that the unidirectional incoherent pumping mode is necessary for the evolution of probe gain.

Tugrul Hakioglu