A detailed study of the quantum coherent and saturating resonances using the hyperfine lines of rubidium
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A detailed study of the quantum coherent and saturating resonances using the hyperfine lines of rubidium Sekhar Dey 1 & Chandan Das 1 & Saswati Dey 1 & Dipankar Bhattacharyya 2 & Biswajit Ray 1 # Springer Nature Switzerland AG 2019
Abstract We have studied both experimentally and theoretically the V-type system in the hyperfine structure of the D1 and D2 lines of rubidium with co-propagating pump-probe laser fields. The experimental observation in the V-type system shows the high contrast EIT peak along with the saturation peaks in the probe Doppler profile. A velocity dependent analysis regarding the formations and frequency positions of the observed resonances has been done. The dependence of the EIT line shape on the variation of the pump laser intensity and detuning has been investigated. It is observed that the EIT resonance disappears for a pump power when it is less than the probe power and the saturating effects dominate over the coherence effects in the system. By properly tuning the pump laser, a perfectly symmetric EIT peak with high contrast is obtained at the center of the probe Doppler profile, while the strong saturating resonances get eliminated. A theoretical model based on the density matrix formulation has been presented corresponding to a five-level V-configuration. This model helps us to interpret the experimental observation theoretically. Keywords Atomic coherence . Optical pumping . Hyperfine transitions . Density matrix . EIT
1 Introduction Electromagnetically induced transparency (EIT) is a quantum optical effect in which an absorptive medium becomes transparent over a narrow frequency range due to the quantum interference between the pump and probe beams. The narrow line shape of the EIT resonance has made it useful for application in high-resolution spectroscopy [1], precision optical magnetometer [2], slow light generation [3, 4], four-wave mixing [5], atomic clock [6], light storage [7], quantum information
* Biswajit Ray [email protected]
1
Department of Physics, University of Calcutta, 92 APC Road, Kolkata 700009, India
2
Department of Physics, Santipur College, WB-741404, Shantipur, India
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processing [8], etc. EIT resonances can be obtained from the basic three-level schemes (TLS), namely the lambda (Λ), vee (V) and cascade (Ξ) type systems. The Λ-type EIT was first demonstrated theoretically by Imamoglu and Harris [9] in 1989 and its first experimental observation was done by Boller et al. [10] in 1991. In the Λ-type system, the pump and probe lasers connect two different ground levels to a common excited level and the coherency is created between the ground levels. The origin of the EIT resonance in the Λ-type system can be explained using the concept of population trapping in the coherently prepared atomic states [11–14]. The Vtype system is formed when the pump and probe laser beams are connected to the different excited levels sharing a common ground level. In this case, the coherency occurs among the excited levels and the decays from
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