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

作者：Chanu Sapam Ranjita; Natarajan Vasant^*

来源：Optics Communications, 2013, 295: 150-154.

DOI：10.1016/j.optcom.2013.01.042

• Electromagnetically induced transparency
• Electromagnetically induced absorption
• Laguerre-Gaussian beam
• Coherent control

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 -%26gt; F%26apos; = 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.

• 出版日期2013-5-15