Abstract We present a theoretical investigation of the electromagnetically induced absorption (EIA) due to transfer of population (TOP) in the double two-level system (TLS). It shows that one TLS is responsible for the sub-natural absorption part of EIA, and the other TLS is responsible for the natural absorption part of EIA. We propose a scheme in which the sub-natural absorption part of EIA is governed by the effect of coherent hole burning (CHB) and achieves an enhancement of at least two orders of magnitude with the detuned coupling field, while the natural absorption part is dominated by the effect of Mollow absorption (MA) and does not change with the detuned coupling field. Due to the effects of CHB and MA, the magnitude of four-wave mixing (FWM) achieves a significant increase for double TLS. We show in detail the evolution of the magnitude of the FWM signal with coupling detuning and Rabi frequency. It is demonstrated that strong resonances occur in the FWM profile at frequencies symmetrically displaced from the frequency of the coupling field by coupling detuning.
Abstract We present a theoretical investigation of the electromagnetically induced absorption (EIA) due to transfer of population (TOP) in the double two-level system (TLS). It shows that one TLS is responsible for the sub-natural absorption part of EIA, and the other TLS is responsible for the natural absorption part of EIA. We propose a scheme in which the sub-natural absorption part of EIA is governed by the effect of coherent hole burning (CHB) and achieves an enhancement of at least two orders of magnitude with the detuned coupling field, while the natural absorption part is dominated by the effect of Mollow absorption (MA) and does not change with the detuned coupling field. Due to the effects of CHB and MA, the magnitude of four-wave mixing (FWM) achieves a significant increase for double TLS. We show in detail the evolution of the magnitude of the FWM signal with coupling detuning and Rabi frequency. It is demonstrated that strong resonances occur in the FWM profile at frequencies symmetrically displaced from the frequency of the coupling field by coupling detuning.
We predict the occurrence of electromagnetically induced absorption (EIA) in cycling degenerate two-level transitions where Fe=Fg+1 and Fg>0, interacting with pump and probe lasers with the same polarization. The EIA is due to transfer of population (TOP) between the Zeeman levels of the ground hyperfine state, rather than transfer of coherence (TOC) which occurs for perpendicularly polarized lasers. We model EIA-TOP using a double two-level system (TLS) which we compare with the four-level N system, which models EIA-TOC. When the pump intensity is low, both models give an EIA peak at line center. The effect of introducing phase-changing collisions is studied, in the presence and absence of Doppler broadening, for both the double TLS and N systems. In the presence of phase-changing collisions, the central EIA peaks are narrowed in both models and persist to higher pump Rabi frequencies than in the absence of collisions. In the double TLS, in the presence of Doppler broadening, the central EIA-TOP peak becomes narrower and does not develop a dip in its center, in contrast to the N system. The central dip that appears in the Doppler-broadened EIA-TOC spectrum can be wiped out by adding phase-changing collisions. We demonstrate that EIA-TOP can be obtained for realistic atomic transitions interacting with lasers that have the same polarization.
Abstract We present a theoretical study of four-wave mixing (FWM) in a degenerate two-level atomic system subject to a magnetic field whose Zeeman sublevels constitute a tripod-type atomic system, which is driven by a linearly polarized field, and coupled and probed by two sets of left and right circularly polarized fields. The optical effects of coherent hole burning (CHB) and electromagnetically induced transparency (EIT) are involved in the coherent system, among which the CHB has much larger response for the FWM than the EITs. Three situations of CHB are involved, and they are the solitary CHB, overlapped CHBs, and an overlap between CHB and EIT. The overlapped CHBs have the greatest magnitude of FWM signal among the three situations. Whereas, for the overlapped CHB and EIT, it has the smallest FWM magnitude, which is no more than one tenth of the former. While for the single CHB, the FWM magnitude is half of that of the overlapped CHBs. It is noted that, in the overlap between CHB and EIT, dual EIAs can be obtained, whose FWM signal also has an enhancement in comparison to no EIA.
The absorption spectrum of a weak probe, interacting with a driven degenerate two-level atomic system, whose ground and excited hyperfine states are Fg,e, can exhibit narrow peaks at line center. When the pump and probe polarizations are different, Fe=Fg+1 and Fg>0, the electromagnetically induced absorption (EIA) peak has been shown to be due to the transfer of coherence (TOC) between the excited and ground states via spontaneous decay. We give a detailed explanation of why the TOC that leads to EIA (EIA-TOC) can only take place when ground-state population trapping does not occur, that is, when Fe=Fg+1. We also explain why EIA-TOC is observed in open systems. We show that EIA can also occur when the pump and probe polarizations are identical and Fe=Fg+1. This EIA is analogous to an effect that occurs in simple two-level systems when the collisional transfer of population (TOP) from the ground state to a reservoir is greater than that from the excited state. For a degenerate two-level system, the reservoir consists of the Zeeman sublevels of the ground hyperfine state, and of other nearby hyperfine states that do not interact with the pump. We will also discuss the four-wave mixing spectrum under the conditions where EIA-TOC and EIA-TOP occur.
Electromagnetically induced transparency (EIT) resonance is obtained in a well-studied lambda three level system where an optical coupling field and a probing field interact with two optical transitions. However, both electromagnetically induced absorption (EIA) and EIT can be obtained in a modified quasi-lambda four level system consisting of an optical-radio two-photon coupling field and a probing field. By solving the density matrix equation of motion, a physical account of EIA and EIT is given in terms of a dressed state picture. It can be seen that the optical coupling field in this quasi-lambda four level system has a crucial effect on the forming of EIA and EIT. An EIA is observed under a resonant optical coupling and it evolves into an EIT when there is a detuning. Furthermore, the width of EIA or EIT increases as the optical coupling Rabi frequency increases.
The transparency and absorption of the Λ-type three-level scheme driven by two coupling fields were investigated.Mollow profile was obtained in a two-level scheme where a strong coupling field and a probing field were applied on the same optical transition between excited state and ground state.There was another coupling field which drived excited state to another ground states hyperfine level in this paper.The Λ-type three-level scheme driven by two coupling fields was introduced,and some new quantum coherent phenomena were given.It can be seen that there is superposition of Mollow profile and electromagnetically induced transparency(EIT) or electromagnetically induced absorption(EIA).The dependence of the position of EIT or EIA on Rabi frequencies and frequency detunings of two coupling fields is investigated.The results can be explained by dressed-state formalism.
Employing an intense laser field coupling to the degenerate two-level system of cesium 6 2S_ 1/2(F=4)- 6 2P_ 3/2(F′=5) transition in a cesium vapor cell, electromagnetically induced absorption (EIA) has been demonstrated via probe absorption spectra, at the same time, electromagnetically induced transparency (EIT) of V-type three-level scheme has been demonstrated on the F=4-F′=3 and F=4-F′=4 transition frequency. The EIA is affected by the intensity and detuning of the coupling laser. By analyzing the effect of optical pumping between Zeeman sub-levels on the EIA and the coherent interactions between multiple degenerate two-level atoms, it is shown that the optical pumping affects the population of different Zeeman sub-levels and the number of the involved two-level atoms, the coherent time between the sub-levels is then changed and the linewidth and intensity of the EIA are affected accordingly.