Electromagnetically Induced transparency with Laguerre-Gaussian laser modes in ultracold rubidium

Abstract

We demonstrate electromagnetically induced transparency (EIT) using lasers in the Laguerre- Gaussian mode. The probe transmission is studied in an ultracold gas for the D2 line in both 85Rb and 87Rb. We consider the Lambda EIT configuration when the control laser is in the Laguerre-Gaussian mode. We compare these results to a similar configuration, but with the control laser in the fundamental laser mode. We model the transmission of a probe laser under both configurations, and we find good agreement with the experiment. We conclude that the use of Laguerre- Gaussian modes in electromagnetically induced transparency results in narrower resonance linewidths as compared to uniform control laser intensity. The narrowing of the linewidth is caused by the spatial distribution of the Laguerre-Gaussian intensity profile. This narrowing is dependent on the relative beam sizes between the control laser and the probe laser. We examine the EIT spectrum character- istics changing parameters of the Laguerre-Gaussian control laser, such as beam waist and Rabi frequency. We found that the EIT resonance is optimized when the Laguerre-Gaussian control and the Gaussian probe have the same waist size. Additionally, the spatial structure of the probe transmission is manipulated us- ing the Laguerre-Gaussian control laser. A control laser in the Laguerre-Gaussian mode is characterized with annular intensity profiles. This results in the increased transmission of the probe in regions of high control intensity, and high absorption in the central, dark region of the Laguerre-Gaussian mode. We transferred the image of the control laser to the probe laser.