Abstract: A laser diode detection and optical pumping cesium resonator in which the frequency of the laser diode is made dependent on a signal delivered by a detector picking up the fluorescence light emanating from an interaction zone created just at the output of the cesium oven by the interaction of the cesium atom jet and a part of the light beam emitted by said detection diode. In particular, a laser diode detection and optical pumping cesium resonator having a cesium oven emitting a flow of cesium atoms, a resonating cavity in the flow path, a laser diode optical pump delivering a light beam into the atom flow between the cavity and the oven at a first interaction zone and a cesium resonance frequency generator. A detector for detecting fluorencence from a second interaction zone at the cavity output resulting from the interaction of the atom stream with a third laser. The detector delivering a signal representative of the second interaction to frequency control means to control the frequency of the generator.