Generation and waveform control of narrow bandwidth paired and single photons

It is well known that electromagnetically induced transparency (EIT) can enhance nonlinear optical processes. In this thesis we show how EIT might be used to modify the properties of parametric down conversion so as to generate narrow-band paired and single photons with high spectral brightness and controlled waveforms.;We also describe our recent experimental efforts aimed at the development of a two dimensional magneto-optical trap with a high optical depth of the atomic cloud. High optical depth enhances a nonlinear interaction between photons and the atomic ensemble so that the photons are generated mostly in pairs. Currently we can get the optical depth as high as 60. This allows us to achieve efficient photon generation with the retrieval efficiency of 75% and correlation times up to 1 mus.;As an interesting application of our narrow band paired photon source, we show how photons may be modulated so as to produce single-photon wave functions whose amplitude and phase are arbitrary functions of time.;We describe the experiments and theory on narrow-band paired photon generation using a third order nonlinear process in cold Rb atoms. With low parametric gain and high optical depth we show that the system can produce highly correlated photon pairs. The shape of the intensity correlation function and the emission bandwidth depend on the intensity of the driving coupling laser and the optical depth of the atomic sample. Compared to the ideal spontaneous parametric down conversion in crystals, we show that paired photon generation in the double-lambda atomic system is affected by Raman gain in the Stokes channel and absorption at the EIT poles in the anti-Stokes channel.