Kanhaiya Pandey

High-resolution hyperfine spectroscopy of excited states using electromagnetically induced transparency

We use the phenomenon of electromagnetically induced transparency in a three-level atomic system for hyperfine spectroscopy of upper states that are not directly coupled to the ground state. The three levels form a ladder system: the probe laser couples the ground state to the lower excited state, while the control laser couples the two upper states. As the frequency of the control laser is scanned, the probe absorption shows transparency peaks whenever the control laser is resonant with a hyperfine level of the upper state. As an illustration of the technique, we measure hyperfine structure in the

Conversion between electromagnetically induced transparency and absorption in a three-level lambda system

7S_{1/2}

Coherent control of magneto-optic rotation

states of

Splitting of electromagnetically induced transparency under strong-probe conditions due to Doppler averaging

^{85}Rb

Resolving closely spaced hyperfine levels in the 3P3/2 state of 23Na

and

A high flux source of cold strontium atoms

^{87}Rb

Role of population transfer under strong probe conditions in electromagnetically induced transparency

, and obtain an improvement of more than an order of magnitude over previous values.

Absolute frequency determination of the 5P3/2-->7S1/2 transition in 87Rb.

We show that it is possible to change from a subnatural electromagnetically induced transparency (EIT) feature to a subnatural electromagnetically induced absorption (EIA) feature in a (degenerate) three-level. system. The change is effected by turning on a second control beam counter-propagating with respect to the first beam. We observe this change in the D-2 line of Rb in a room temperature vapor cell. The observations are supported by density-matrix analysis of the complete sublevel structure including the effect of Doppler averaging, but can be understood qualitatively as arising due to the formation of N-type systems with the two control beams. Since many of the applications of EIT and EIA rely on the anomalous dispersion near the resonances, this introduces a new ability to control the sign of the dispersion. Copyright (C) EPLA, 2012

Linear and nonlinear magneto-optical rotation on the narrow strontium intercombination line

We experimentally study the rotation of the plane of polarization of a laser beam passing through room-temperature Rb vapour. The rotation occurs because the medium behaves differently for the two orthogonally-polarized components, displaying what is known as circular birefringence or linear dichroism. The difference is induced either by a control laser applied to an auxiliary transition of a ladder-type system, or by an applied axial magnetic field. In the presence of both control laser and magnetic field, the line shape shows an interesting interplay between the two effects with regions of suppressed and enhanced rotation. The line shapes can be understood qualitatively based on a density-matrix analysis of the system.

Polarization-rotation resonances with subnatural widths using a control laser

We study the phenomenon of electromagnetically induced transparency (EIT) in room-temperature Rb vapour under conditions of a strong probe laser. The atoms form a ladder system with the lower transition coupled by the probe laser and the upper transition coupled by the control laser. Density-matrix analysis of the system shows that, for zero-velocity atoms, the strong probe beam causes a reduction in absorption and broadening of the profile. But the lineshape after thermal averaging shows a splitting of the EIT resonance and enhanced absorption near line centre. The experimental observations in