In a three-level atomic system, when on resonance light (the “probe”) impinges on the atoms, the light is strongly scattered from the atoms, and the amount of light to exit the vapor cell exponentially decreases with atom density. If, however, a second laser beam (the “pump”) which radiatively couples a different ground state and the same excited state, is added to the system, the probe beam will pass without absorption. This phenomenon is know as Electromagnetically Induced Transparency (EIT). The window of transparency can be very narrow, and thus exhibit striking dispersive characteristics, make EIT a candidate for multiple experimental realization of everything from atomic clocks, to light storage media.

Typical EIT level configurations.

Unlike typical EIT experiments, which utilize alkali vapor cell (typically Rb), we are currently (in collaboration with the Katz group at the Hebrew University) constructing an experimental realization of EIT in a metastable neon cell. Whereas in the alkali experiments, noble gases are typically used as a “buffer” gas to cool the alkali atoms, in our case, we expect the ground state neon atoms to act as a buffer gas to the metastable atoms. An additional benefit to using neon is that for the even (and more common) neon isotopes (20 and 22) the optical transition we will probe is a closed transition, so that we expect no radiative losses to states other then the ground state (we expect the metastable state lifetime to be on the order of 100s of ms, and are currently measuring it as a function of pressure).

A picture of our EIT cell, the plasma is generated by RF excitation, some of the electrons
in the plasma are recaptured into the metastable state. This is not Neon yet, the blue glow
is characteristic of the nitrogen in the residual air in the cell.

Recently we’ve also started discussing the complementary process, Electromagnetically Induced Absorption (EIA) in which the absorption of a beam is enhanced in the medium by the interaction with the pump beam. We are currently working on an experiment to measure both processes and transition between them. We are also looking into magnetometry using the neon atoms, by detecting Faraday rotation in the neon vapor induced by external magnetic fields.