Negative Refraction in Rare-Earth Doped Crystals

In this project, our long-term goal is to demonstrate the first negative refraction in atomic systems. Although the concept of negative refraction remained an academic curiosity for a long time, it is now well-understood that negative refraction may have important and far-reaching practical implications. The key challenge in observing negative refraction in the optical region of the spectrum is the weakness of the magnetic response. Our central experimental result during this project has been the first observation of Rabi flopping of a magnetic dipole transition in the optical region of the spectrum. We have performed this experiment using the 7F0-5D1 transition of europium ions in a cryogenically cooled doped crystal. This is a major result; we have shown for the firs time that an electron can interact sufficiently strongly with the magnetic field of a light wave and coherently move between the levels. Another important result during this project was the proposal for a new type of materials that exhibit negative refraction. Because of these achievements, observing negative refraction and left-handed electromagnetic waves in atomic systems seem within reach for the first time.