Light and magnetic field induced coherence effects in atoms

Abstract

In this thesis, we have studied the coherence effects in atoms induced by light and a magnetic field. After giving an introduction to the contents of the thesis, details about the theory and the experimental setup used are given. The next few chapters contain the experimental results backed by a theoretical understanding. Only the joint work with the Armenian group (paper titled “Study of EIT resonances in an anti-relaxation coated Rb vapor cell” published in Physics Letters A) is one where they did the experiment and we did the theory. The thesis ends with a discussion about the various results presented. In the first work, the magnetic field induced coherence effect is studied in the light of the Hanle effect. We have studied the transformation of a Hanle EIT to a Hanle EIA for a circularly polarized beam in presence of a spatially separated control beam whose ellipticity is varied. A density matrix model describing three regions of interaction is developed to reproduce the experimental results. The second work describes the use of CPT/EIT system in a double-lambda configuration to interfere beams in one lambda system while the other lambda system acts as a phase reference. This process of light interference mediated by atomic coherence is extended to propose a system in which interference between two beams 10s of GHz apart in frequency could be detected on a low bandwidth (10s of MHz) optical detector. The third work describes an observation of EIA in a vee + ladder system in 87Rb. The vee system is formed by using the D1 line of 87Rb as control and the D2 line as the probe, and the ladder system is formed by the same probe as in vee system and a beam on the transition from 5P3/2 to 5D5/2 as control. The fourth work, done along with our collaborators in Armenia, shows splitting of EIT into dark and bright resonance in the presence of a strong transverse magnetic field in an anti-relaxation coated cell in the D1 line of 87Rb. We have performed a density matrix analysis using all the magnetic sublevels to reproduce the experimental results. The tunability of such a system between super-luminal and sub-luminal propagation for a probe beam is also theoretically discussed.