title: Three-photon electromagnetically induced transparency using Rydberg states.
abstract: We demonstrate electromagnetically induced transparency in a four-level cascade system where the upper level is a Rydberg state. The observed spectral features are sub-Doppler and can be enhanced due to the compensation of Doppler shifts with AC Stark shifts. A theoretical description of the system is developed that agrees well with the experimental results, and an expression for the optimum parameters is derived.
authors.affiliation: Joint Quantum Centre Durham-Newcastle, Department of Physics, Durham University, Durham, England, UK.
authors.forename: Christopher
authors.initials: C
authors.lastname: Carr
authors.forename: Monsit
authors.initials: M
authors.lastname: Tanasittikosol
authors.forename: Armen
authors.initials: A
authors.lastname: Sargsyan
authors.forename: David
authors.initials: D
authors.lastname: Sarkisyan
authors.forename: Charles S
authors.initials: CS
authors.lastname: Adams
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Weatherill