Room temperature Zeeman EIT in a hot vapor of ⁸⁷Rb atoms using a D₂-line transition

The quantum interference phenomenon, known as electromagnetically induced transparency (EIT), renders a medium transparent to a weak probe beam at resonance in the presence of a strong coupling beam. In this study, we experimentally observed Zeeman EIT considering the D₂ line of ⁸⁷Rb atoms in a closed system, focusing on the transition to using orthogonally co-propagating, circularly polarized strong coupling (σ⁺) and weak probe (σ^-) beams. Our aim is to observe the impact of coupling intensity, probe beam diameter, and Rb cell temperature on EIT line width. Two external cavity diode lasers (ECDLs), tuned to a wavelength of 780.24 nm are used to generate the beams. Lenses were employed to adjust beam diameters before the Rb cell, while a combination of a half-wave plate (HWP) and polarizing beam splitter (PBS) controlled intensity. A quarter-wave plate (QWP) converted the linearly polarized beam to circular polarization. To lock the coupling beam to the desired transition, a portion of it was used to obtain the saturated absorption spectroscopy (SAS) signal, while the probe beam was scanned to observe EIT features. A narrow EIT line width of ~1 MHz was achieved with a beam diameter of 3.5 mm at a temperature of 300 K.