Probe amplification from Raman gain to inversionless gain

Aaron S. Manka, Michael Scalora, Jonathan P. Dowling +1 more

Christoph H. Keitel, Olga A. Kocharovskaya, L. M. Narducci +3 more

We analyze the physical origin of the inversionless amplification in four-level atoms driven by a Raman field and identify the existence of two different mechanisms for the predicted gain. The first mechanism is connected with the appearance of a population inversion between the atomic states dressed by the coherent pump, while the second is linked to the buildup of coherence among these states. Proper selection of the relaxation parameters can make either the first or the second mechanism dominant over the other although usually both coexist.

Jérôme J.-P. Leon, А. В. Михайлов

Michael D. Duncan, John F. Reintjes, Lawrence L. Tankersley +2 more

Jin‐Hui Wu, Jin-Yue Gao

Due to interaction with the vacuum of the radiation field, near-degenerate lower levels in a $\ensuremath{\Lambda}$ system have an additional coherence term, the spontaneously generated coherence term. In this paper, we investigate effects of spontaneouly generated coherence on inversionless gain in the presence of a weak probe, a strong coherent field, and an incoherent pump. We find that the inversionless gain stems from both spontaneously generated coherence and dynamically induced coherence, but the former contributes more to the inversionless gain. In particular, we can modulate the inversionless gain just by changing the relative phase between the two fields.

Benjamin Fain, Vadim Khidekel, S. H. Lin

The pump pulse creates nonstationarity and coherence in the medium. The amplification (absorption) of the probe pulse in the nonstationary coherent medium belongs to phase-dependent Raman amplification (absorption). In this inversionless mechanism of amplification the phase is determined by the delay time between the pump and the probe pulses.