Transfer-of-coherence-enhanced stimulated emission and electromagnetically induced absorption in Zeeman split F_g-->F_e=F_g−1 atomic transitions

Abstract

The probe absorption spectra in single and multiple tripod systems formed when a weak sigma polarized pump and a tunable pi polarized probe interact with a Zeeman split F(g)-->F(e)=F(g)-1 atomic transition are characterized by two interfering stimulated Raman features separated by an electromagnetically induced absorption (EIA) peak at the line center. These Raman features can appear as either sharp stimulated emission peaks or electromagnetically induced transparency windows. In the multitripod systems, the EIA and stimulated emission peaks derive from the combined effects of interference between the stimulated Raman features and transfer of coherence from the excited to ground states.

Interacting double dark resonances in a hot atomic vapor of helium

“…The separation between the two dark resonances varies linearly with the applied magnetic field. The double dark resonance cannot be explained in terms of transfer of coherence from the excited level to the ground level [16,23] but these dark resonances are two EIT peaks at δ = ±∆ Z . When the coupling power is increased in the presence of the magnetic field, an absorption line appears, much narrower and deeper than that found in the first configuration, which is the signature of an interference phenomenon between the two induced EIT windows [3,18].…”

“…As the number of excited states is less than the number of ground states, transfer of coherence does not play any role [22]. Thus these double dark resonances are not stimulated Raman peaks [16,23] but detuned EIT peaks, interfering destructively with each other leading to an absorption dip in-between for non-zero magnetic fields. We model the system successfully and verify our experimental results.…”

Effects of thermal motion on electromagnetically induced absorption

“…It has been shown [6,7,9], that the EIA peak is due to transfer of coherence (TOC) from the excited state to the ground state, via spontaneous emission. The excitedstate coherence only exists in systems where the coherent population trapping is incomplete so that there is some population in the excited state [9,10]. The transfer of this coherence to the ground state leads to a peak in the contribution of the ground-state two-photon coherence to the probe absorption at line center, instead of the dip that occurs in its absence (for example, in a Λ system or a non-degenerate N system) [11].…”

Interacting double dark resonances in a tripod system of room-temperature4He

“…In this case, two dark resonance peaks appear and they shift from the zero detuning position with increasing magnetic field. The double dark resonance cannot be explained in terms of transfer of coherence (TOC) from the excited level to the ground level 21,22 but these dark resonances are two EIT peaks at = Δ Z . For different coupling powers at a given magnetic field, these two peaks interfere with each other 5 .…”