Electromagnetically induced transparency (EIT) in multilevel atomic systems exhibits complex dependencies on optical depth (OD) and polarization configurations, yet their combined effects remain underexplored. Here, we introduce a dissipation factor $\ensuremath{\kappa}$ which quantifies polarization-dependent absorption resulting from the emergence of dissipative channels. Starting from a semiclassical framework, we derive the transmission of a resonant probe as ${T}_{\text{res}}=exp(\ensuremath{-}\ensuremath{\kappa}\ifmmode\cdot\else\textperiodcentered\fi{}d)$, where
d denotes the optical depth, demonstrating that $\ensuremath{\kappa}$ and OD jointly govern the transparency. And broadly, $\ensuremath{\kappa}$ is universally applicable across any multilevel system when its value spans a range $\ensuremath{\kappa}\ensuremath{\in}[0,1]$, where $\ensuremath{\kappa}=0$ corresponds to ideal transparency and $\ensuremath{\kappa}=1$ represents pure absorption. Our experimental results in cold
87Rb atomic ensemble across low and high OD regimes confirm the completeness of the theoretical model, with EIT line shapes showing close agreement with simulations. By elucidating the joint effects of OD and polarization-dependent dissipation in EIT, this work is conducive to systemic optimization in multilevel EIT systems such as quantum memory, optical switching, and precision metrology applications.
We have theoretically and experimentally investigated the V-type three-level system in hot sodium atomic vapor interacting with two optical waves: probe, resonant to the D1 line, and coupling, the D2 line. Theoretically, probe transmission spectra are simulated by using a perturbative treatment including eight hyperfine levels (multilevel system) in the 3S1/2, 3P1/2, and 3P3/2 states. The spectra are composed of linear absorption, saturated absorption, and electromagnetically induced transparency (EIT) signals. By comparing this simulation with the experimental results, we concluded that we have indeed observed EIT signals when the coupling beam is resonant to the D2-line closed transition.
We calculate the line shape and linewidths for electromagnetically induced transparency (EIT) in optically thick, Doppler broadened media (buffer gasses are also considered). In generalizing the definition of the EIT linewidth to optically thick media, we find two different linewidth definitions apply depending on whether the experiment is pulsed or continuous wave (cw). Using the cw definition for the EIT line shape we derive analytic expressions describing the linewidth as a function of optical depth. We also review the EIT line shapes in optically thin media and provide physical arguments for how the line shapes change as a function of various parameters.