Coherent atom-light interactions in multi-level systems

This thesis presents work on experiments performed using electromagnetically induced transparency (EIT) in Rubidium vapour cells. Starting with a simple three-level Λ-system, extra complexity is introduced by adding an additional control beam. This makes the switching from narrow transmitting resonances to absorbing resonances possible. Rydberg EIT is then introduced and is used to shown how the switching of such resonances using external electric fields in possible. The work then progresses towards the use of thin vapour cells to overcome the limitations of conventional systems. In the transition to thin vapour cells, the role of dipole interactions in Rydberg atoms motivates the idea of an atomic quantum dot. The Kerr effect is then characterised and used to perform phase modulation in a gas. The Rydberg state itself is then phase modulated and this is shown to give rise to frequency sidebands which offer a promising way of determining dc electric fields.