Precision measurements with coherent dark resonances

Summary form only given.We consider coherent dark resonances in Cs vapor cells where the effective interaction time between atoms and light is increased through the addition of a buffer gas or through a coating of the cell walls with siloxane. The light sources are two diode lasers phase locked at 9.2 GHz frequency difference, corresponding to the hyperfine splitting of cesium. The phase-locked loop eliminates difference frequency jitter and leads to resonances narrower than 50 Hz, which can be applied to various precision experiments.