2011/10/29 by Sapam Ranjita Chanu, Chanu, Sapam Ranjita, Vasant Natarajan +1
Physics and Astronomy · #Quantum optics and atomic interactions #Cold Atom Physics and Bose-Einstein Condensates #Mechanical and Optical Resonators
paper · pdf · doi:10.48550/arxiv.1110.6499
We study the phenomenon of electromagnetically induced transparency and\nabsorption (EITA) using a control laser with a Laguerre-Gaussian (LG) profile\ninstead of the usual Gaussian profile, and observe resonances with width up to\n20 times below the natural linewidth. Aligning the probe beam to the central\nhole in the doughnut-shaped LG control beam allows simultaneously a strong\ncontrol intensity required for high signal-to-noise ratio and a low intensity\nin the probe region required to get narrow resonances. Experiments with a\nsecond-order LG beam show that transit time and orbital angular momentum do not\nplay a significant role. This explanation is borne out by a density-matrix\nanalysis with a radially varying control Rabi frequency. We observe these\nresonances using degenerate two-level transitions in the D2 line of Rb in a\nroom temperature vapor cell. We show that the linewidth is reduced by about a\nfactor of 4 compared to the use of a Gaussian control beam, which should prove\nadvantageous in all applications of EITA and other kinds of pump-probe\nspectroscopy.\n