Narrowing of resonances in electromagnetically induced transparency and absorption using a Laguerre-Gaussian control beam

Chanu, Sapam Ranjita and Natarajan, Vasant (2013) Narrowing of resonances in electromagnetically induced transparency and absorption using a Laguerre-Gaussian control beam. In: Optics Communications, 295 . pp. 150-154.

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Abstract

We study the phenomenon of electromagnetically induced transparency and absorption (EITA) using a control laser with a Laguerre-Gaussian (LG) profile instead of the usual Gaussian profile, and observe significant narrowing of the resonance widths. Aligning the probe beam to the central hole in the doughnut-shaped LG control beam allows simultaneously a strong control intensity required for high signal-to-noise ratio and a low intensity in the probe region required to get narrow resonances. Experiments with an expanded Gaussian control and a second-order LG control show that transit time and orbital angular momentum do not play a significant role. This explanation is borne out by a density-matrix analysis with a radially varying control Rabi frequency. We observe these resonances using degenerate two-level transitions in the D-2 line of Rb-87 in a room temperature vapor cell, and an EIA resonance with width up to 20 times below the natural linewidth for the F = 2 -> F' = 3 transition. Thus the use of LG beams should prove advantageous in all applications of EITA and other kinds of pump-probe spectroscopy as well.

Item Type:	Journal Article
Publication:	Optics Communications
Publisher:	Elsevier Science
Additional Information:	Copyright of this article belongs to Elsevier Science.
Keywords:	Electromagnetically Induced Transparency; Electromagnetically Induced Absorption; Laguerre-Gaussian Beam; Coherent Control
Department/Centre:	Division of Physical & Mathematical Sciences > Physics
Date Deposited:	28 May 2013 11:25
Last Modified:	28 May 2013 11:25
URI:	http://eprints.iisc.ac.in/id/eprint/46562

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