The effects of neighboring transitions through Doppler broadening on electromagnetically induced absorption (EIA) and electromagnetically induced transparency (EIT) for the D2 transition line in Rb atoms with respect to the same circular polarization configurations ( σ + − σ + ) of coupling and probe lasers have been investigated. Spectra for the open F g = 2 → F e = 2 transition of 87 Rb and the F g = 3 → F e = 2 and 3 transitions of 85 Rb exhibit EIA, resulting from the neighboring effect of F g = 2 → F e = 3 and F g = 3 → F e = 4 transitions, respectively. In contrast, EIT is observed for the open F g = 2 → F e = 1 transition of 87 Rb, which indicates greater hyperfine energy splittings of 87 Rb and weaker neighboring effects than those of 85 Rb. Based on the theoretical results, we can confirm that EIT in the case of F g > F e for 87 Rb and circular parallel polarization transforms into EIA due to the magnitude of the neighboring effects with a decrease in the hyperfine energy splittings.
Electromagnetically induced absorption (EIA) in a degenerate closed transition was measured under the action of a probe and a coupling laser of various polarizations giving rise to different possible N-systems or multi-level systems. While the probe shows EIA the coupling is mainly characterized by “absorption within transparency”. However, for certain lasers' intensity ranges, a switch between “absorption within transparency” and “transparency within transparency” in the coupling absorption spectra was measured for the first time.
After the discovery of electromagnetically induced absorption (EIA), both theoretical and experimental research was performed to explain not only the probe laser absorption and dispersion spectra, but also those of the coupling laser. The investigations of EIA in degenerate two-level systems have often been realized using two linearly polarized lasers of orthogonal polarization [1]. However, the simplest configuration leading to EIA is the so-called N-system [2] which basically requires the simultaneous adoption of a circularly polarized coupling laser and a linearly polarized probe (here called σ−π). To our knowledge, no experimental measurements of the coupling laser exist in the configurations (σ+−σ−, π−σ− or σ+−π).
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.
In this paper, we present a theoretical model for studying the interaction between linearly polarized laser light and near-degenerated Zeeman sublevels for a multiple V-type atomic system of $^{2}S_{1∕2}{F}_{g}=2\ensuremath{\rightarrow}^{2}P_{3∕2}{F}_{e}=3$ transition in
87Rb. We have calculated the laser absorption in a Hanle configuration, as well as the amplitudes and the widths of electromagnetically induced absorption (EIA) in the range of laser intensities from
0.01to40mW∕cm2. Our results, showing nonvanishing EIA amplitude, a nonmonotonic increase of the EIA width for the increase of laser intensity, and pronounced shape differences of the Hanle EIA curves at different laser intensities, are in good agreement with recent experimental results. We have found that the EIA behaves differently than the electromagnetically induced transparency (EIT) as a function of the laser intensity. Both the amplitude and width of the EIA have narrow maximums at
1to2mW∕cm2. We have shown the strong influence of Doppler broadening of atomic transition on Hanle resonances and have suggested the explanation of it.
Spontaneous transfer of coherence has proven to be a good interpretative scheme for the explantation of the spectra of a probe laser probing a closed degenerate two-level systems. With its aid it was possible to give an explanation for the emergence of electromagnetically induced absorption and also to make predictions on the associated coupling laser spectra. Here we extend our work on the role of the coupling laser in electromagnetically induced absorption presenting new measurements of the probe and coupling laser absorption and dispersion spectra - taken in the D2 line of caesium - which reassert the importance of spontaneous transfer of coherence in the generation of electromagnetically induced absorption spectra. All measurements were performed with linearly polarised coupling and probe laser of orthogonal polarisation, acting on a perpendicularly propagating caesium atomic beam to minimise the Doppler broadening of the lines. For sake of completeness we compared the electromagnetically induced absorption spectra with electromagnetically induced transparency spectra obtained in another two-level system within the same line. The measured probe spectra were used to calculate the refractive index of caesium in the presence of electromagnetically induced transparency and absorption. On that basis we could calculate the effect of Kerr nonlinearities and measure nonlinear Kerr coefficients of the order of n2 ≈ 10-5 cm2/mW with absorption coefficients of the order of &agr; ≈ 0.1 cm-1.