We report characterization of EIT resonances in the D1 line of Rb 87 under various experimental conditions. The dependence of the EIT linewidth on the power of the control field investigated. Strictly linear behavior between the ground levels as the main source of decoherence. We therefore formulated a new theory assuming pure dephasing to be the main decoherence mechanism. We also performed experiments where we created additional decoherence mechanisms by means of a counter-propagating repumper field. This field caused the ground-state population exchange, thus reproducing conditions in which the original theory is valid.
We have theoretically studied the atomic populations, electromagnetically induced transparency (EIT), and dispersion in a three-level Λ-type system. The density matrix equations are set up with regard for the relaxation of populations of the ground states, and the optical Bloch equations are solved analytically in the weak probe field approximation. Decoherence effects in the ground and excited states on the EIT line shape and dispersive signals are studied, and it is found that the EIT line width increases and the peak height decreases, as the decoherence rates increase in the ground and excited states. On the other hand, we have observed that the dispersive signals are steeper and of high contrast for the lower decoherence rates in the ground and excited states. We have also analyzed the variations of atomic populations of the energy levels at the pump Rabi frequency, as well as the decoherence rate in the ground state.
We report electromagnetically induced transparency (EIT) in cold 85 Rb atoms, trapped in the lower hyperfine level F = 2, of the ground state 5 2 S 1/2 (Tiwari V B et al 2008 Phys. Rev. A 78 063421). Two steady-state Λ-type systems of hyperfine energy levels are investigated using probe transitions into the levels F ′ = 2 and F ′ = 3 of the excited state 5 2 P 3/2 in the presence of coupling transitions F = 3 → F ′ = 2 and F = 3 → F ′ = 3, respectively. The effects of uncoupled magnetic sublevel transitions and coupling field's Rabi frequency on the EIT signal from these systems are studied using a simple theoretical model.
Abstract We report the observation of electromagnetically induced transparency (EIT) in a six-level Λ -type system in atomic Rb vapor containing both 87 Rb and 85 Rb. The experimental observation includes five velocity selective optically pumped (VSOP) absorption dips for both 87 Rb and 85 Rb. The EIT signal appears on the background of one such VSOP absorption dips. The measured EIT linewidth ( ) shows sub-natural ( ) values for both lower and higher values of pump Rabi-frequencies. The density matrix based theoretical model for the six-level system is developed and solved numerically by taking into account the Doppler broadening. A complete analytical solution (non perturbative) for a three level Λ -type system has been obtained and compared with the experimentally observed sub-natural EIT linewidth. The simulated spectra are in good agreement with the experimental findings.
We report the experimental investigation of electromagnetically induced transparency (EIT) in a Zeeman-sublevels Λ -type system of cold 87 Rb atoms in free space. We use the Zeeman substates of the hyperfine energy states 5 2 S 1/2 , F = 2 and 5 2 P 3/2 , F ' = 2 of 87 Rb D 2 line to form a Λ -type EIT scheme. The EIT signal is obtained by scanning the probe light over 1 MHz in 4 ms with an 80 MHz arbitrary waveform generator. More than 97% transparency and 100 kHz EIT window are observed. This EIT scheme is suited for an application of pulsed coherent storage atom clock (Yan B, et al. 2009 Phys. Rev. A 79 063820).
Comparison of Electromagnetically Induced Transparency (EIT) Spectra for Six-level Lambda
Λ and Five-level V-type Systems
Electromagnetically induced transparency (EIT) is experimentally studied in a rubidium vapour cell (without buffer gas, both
87Rb and
85Rb present according to their natural abundance) kept within two-layers of
μ(μ)-metal shields to avoid the effect of Earth's magnetic field on the energy levels of atomic rubidium. An external cavity diode laser (ECDL), used as a low power probe laser, is locked to the hyperfine cross-over peak of
F=2→F′=2,3 transitions of
87Rb. The frequency of another ECDL, the pump laser, is set to scan the
F=1→F′=0,1,2 transitions of
87Rb. These form the
Λ-type six level system. In the V-type system, both the pump and the probe lasers share the same
F=2 ground level. The probe beam coming out of the cell is detected by a low noise fast photodetector. The resulting spectra show signature of EIT in the "peak" for the
Λ-type system and in the "dip" for the V-type system. Numerical calculation based simulated spectra are also compared with the experimental spectra. In both the cases very narrow EIT linewidth
(Γt<Γ) is observed even at high value of pump Rabi-frequency
(Ωc≫Γ). Narrower value of EIT linewidth is due to Doppler averaging phenomena.