Electromagnetically Induced Transparency from a Single Atom in Free Space

In this Letter, we report an absorption spectroscopy experiment and the observation of electromagnetically induced transparency from a single trapped atom. We focus a weak and narrow band Gaussian light beam onto an optically cooled (138)Ba(+) ion using a high numerical aperture lens. Extinction of this beam is observed with measured values of up to 1.35%. We demonstrate electromagnetically induced transparency of the ion by tuning a strong control beam over a two-photon resonance in a three-level Lambda-type system. The probe beam extinction is inhibited by more than 75% due to population trapping.