Electromagnetically induced transparency line shapes for large probe fields and optically thick media

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.