Richard R. Moseley

Two-photon effects in continuous-wave electromagnetically-induced transparency

Electromagnetically-induced transparency (EIT) in a cascade three-level scheme is studied in rubidium vapour using continuous-wave titanium sapphire lasers. A counter-propagating experimental configuration significantly reduces the coupling laser power requirements and a reduction in absorption of over 90% is observed. The hyperfine structure of the upper level is seen within the EIT feature and the application of EIT to high-resolution two-photon spectroscopy is discussed. Simultaneous measurements of the excitation to the upper state are presented and clearly show Autler-Townes splitting and power broadening.

Effects of Zeeman splitting on electromagnetically-induced transparency

Abstract An experimental and theoretical study of the effects of Zeeman splitting on electromagnetically-induced transparency in rubidium vapour has been carried out using two single-frequency, continuous-wave Ti:sapphire lasers. We show that a magnetic field, as weak as 80 Gauss, is enough to split the original, zero field, E.I.T. window into distinct sub-components. The number of sub-components observed depends directly on the two-photon selection rules. At the same time, each E.I.T. sub-component experiences a reduction in depth and an increase in broadening which is dependent on the strength of the applied magnetic field.

Enhanced conversion efficiency in three-wave mixing via electromagnetically reduced fundamental wave absorption

Abstract A three-level atomic scheme for resonantly enhanced sum frequency mixing is considered within which strong absorption of a fundamental input wave is the limiting factor on conversion. It is shown that for the case where the other input field is sufficiently strong to cause electromagnetically induced transparency so reducing this parasitic absorption, there is still a significant second order susceptibility, and moreover the efficiency of the nonlinear process is greatly increased in the doppler broadened regime.

Local field effect in the three-level atom

Abstract The density matrix evolution for a three-level cascade atom is generalised to high vapour densities by the inclusion of the local field effect, and thereby, nonlinear cross-coupling terms arise. Numerical results show that these do not affect electromagnetically induced transparency significantly at moderate densities. Opportunities for experimental observation of the correction in this, and a resonantly-enhanced sum frequency mixing system, at very high densities, are indicated.

Lasing turned upside-down

Absorption and emission are two of the most fundamental processes in optics. Fluorescent lights, lasers and all forms of spectroscopy are based on a thorough understanding of these two processes. In recent years, however, a new generation of experiments has been pioneered in which samples that are expected to absorb radiation do not, and samples that are not expected to lase might soon do so. These new phenomena are based on the exploitation of quantum interference within atoms, and challenge much of the conventional wisdom of quantum electronics.