Absorption and dispersion in atomic vapours : applications to interferometery
Continuous wave extended cavity diode lasers are used to measure the absorptive and dispersive properties of the 5 2S1/2 → 5 (^2)Рз/2 resonance, at 780 nm, in Rubidium (Rb) vapour. The Doppler-broadened hyperfine transitions are studied both with and without a pump beam. The investigation concentrates on three-level Л-systems, realized in the presence of a pump beam, exhibiting Electromagnetically Induced Transparency (EIT). Electromagnetically Induced Absorption (EIA) IS also seen. The EIT and EIA resonances can be several orders of magnitude narrower than the natural line width of the atomic transitions in the absence of the pump beam. Further, the EIT resonances are sensitive to applied magnetic fields. The narrowest resonances measured in this work have a full-width at half- maximum of 〜 80 kHz. This is limited by the transit time of the atoms through the probe and pump beams. Predictions of theoretical calculations and models are compared to experimental results. The theory of beam splitters and interferometers is developed to enable the implementation of a Sagnac interferometer in a novel "biased" alignment. This allows the dispersion of atomic resonances to be measured directly. The direct measurement of the dispersion of the narrow EIT features in a "biased" Sagnac interferometer is presented. Such a signal is ideally suited to precision measurement applications such 88 inertial sensing and magnetometry.