Continuous-wave electromagnetically induced transparency: A comparison of V, Λ, and cascade systems

A theoretical and experimental investigation has been carried out into the viability of V-type, Λ-type, and cascade systems within rubidium for the observation of electromagnetically-induced transparency (EIT). A Λ-type system is also discussed where EIT is induced on a two-photon transition. Continuous-wave single-frequency titanium sapphire lasers have been employed to provide the applied optical fields. It is found that systems that have a strong coupling field resonant with the 5${\mathit{S}}_{1/2}$ ground state suffer from complicating optical pumping mechanisms that tend to mask EIT windows. It is also found that wavelength matching of the applied optical fields enhances the observation of EIT since this results in a reduced residual Doppler linewidth of the atomic system.