Electromagnetically induced transparency with Rydberg atoms inside a high-finesse optical cavity*

We present experimental work on the observation of Rydberg electromagnetically induced transparency (EIT) inside a high-finesse optical cavity. We show that a cold atomic cloud with controllable number of atoms can be transported into the cavity by using a focus-tunable lens. Rydberg atoms are excited via a two-photon transition in a ladder-type EIT configuration. A three-peak structure in the cavity transmission can be observed when Rydberg EIT atoms are generated inside the cavity. The two side peaks are caused by ``bright state polaritons'', while the central peak corresponds to a ``dark-state polariton'' The cavity Rydberg EIT system can be useful for single photon generation using the Rydberg blockade effect, studying many-body physics, and generating novel quantum states amongst many other applications.