Laser spectroscopy experiments are reported on rubidium atoms by using two or three external cavity diode lasers to study multiple resonance transitions in Λ- and V-type systems as well as on (Λ+V)-type system. Electromagnetically induced transparency (EIT) peaks having sub-natural line-widths are found on the Doppler broadened transmission backgrounds with velocity selective enhanced absorption dips. In the presence of a pump laser, probe spectrum shows enhancement of EIT signal by tuning the control laser frequency when the Λ- and V-type EIT signals are made to overlap. Theoretical analysis is carried out by solving the optical Bloch equations for five-level atomic model under Λ configuration. With the numerically simulated spectra, variation of EIT transmission peak with ground state decay rate and excited state spontaneous decay rate are investigated. Effect of pump Rabi frequency on the transmission peak is also shown.
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.
Abstract Coherent probe field (L A ) propagation through an eight-level inverted Y-type atomic system, in the presence of two additional coherent radiation fields termed the field L C (control or pump field) and the field L B (repump field), is investigated by using the parameters of 87 Rb 5 S 1 / 2 → 5 P 3 / 2 → 7 S 1 / 2 transitions. The system has two ground energy levels, four intermediate energy levels, and two uppermost energy levels. A theoretical model based on the density matrix method is used for numerical simulation of the probe response under different conditions. Simulated probe absorption spectra under a Doppler-free condition as well as under thermal averaging exhibit electromagnetically induced transparency (EIT). The position and line shape of this EIT profile change with different detunings of the control and repump fields. When the three coherent fields share a common level, a funnel-like EIT window appears in the simulated probe absorption curve. Velocity selective optically pumped absorption peaks are seen in the simulated probe response at room temperature.
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.
Variations of the coherent resonance, i.e. an electromagnetically induced transparency (EIT) peak with the cell temperature in Λ- and V-type systems are observed for the 85 Rb-D 2 transition. In a Λ-type system, the amplitude of the EIT peak gradually decreases and it is finally masked by the broadened optical pumping dips with the increase of the cell temperature. But for the V-type system, the EIT and the saturation peaks are greatly enhanced with the increase of the cell temperature. The effect of the external magnetic field on the EIT resonance is also investigated considering both types of systems. For the Λ-type system in place of a single EIT resonance, five transparency windows with broadened width and reduced contrast are obtained depending on the Zeeman levels formed by the applied magnetic field. In the V-type system, the coherent resonance peak could not be resolved in the presence of the external magnetic field, but a greater number of saturation peaks with broadened width appear in the probe transmission spectrum. A theoretical model is adopted to represent the experimental results. Good agreement is found between the experimental and numerically simulated results.