Transformation of the coherent population trapping resonance into enhanced fluorescence in a paraffin coated Rb vacuum cell

The ultra-narrow resonances achieved in coherent spectroscopy of alkali atoms originate from the destruction of the laser-induced coherence in the ground state. An anti relaxation cell coating preserves the coherence created and, consequently, the resonance narrows by almost two orders of magnitude. Coherence resonances are used in magnetic field sensors, atomic clocks, quantum informatics, ets. In this work, we investigate the features of the CPT resonance on the D1 87 Rb line obtained in fluorescence in paraffin coated cells. The transformation from a black to a bright resonance is found to depend on the laser power and the experimental geometry.