Distinguishing coherent atomic processes using wave mixing

We are able to clearly distinguish the processes responsible for enhanced low-intensity atomic Kerr nonlinearity, namely coherent population trapping and coherent population oscillations in experiments performed on the Rb D1 line, where one or the other process dominates under appropriate conditions. The potential of this new approach based on wave mixing for probing coherent atomic media is discussed. It allows the new spectral components to be detected with sub-kHz resolution, which is well below the laser linewidth limit. Spatial selectivity and enhanced sensitivity make this method useful for testing dilute cold atomic samples.

Broadband optical delay with large dynamic range using atomic dispersion

We report on a tunable all-optical delay line for pulses with optical frequency within the Rb $D_2$ absorption line. Using frequency tuning between absorption components from different isotopes, pulses of 10 ns duration are delayed in a 10 cm hot vapour cell by up to 40 ns while the transmission remains above 10%. The use of two isotopes allows the delay to be increased or decreased by optical pumping with a second laser, producing rapid tuning over a range of more than 40% of the initial delay at 110$^{circ}$C. We investigate the frequency and intensity ranges in which this delay line can be realised. Our observations are in good agreement with a numerical model of the system.