A frequency-stabilized laser source that is adapted for use as a frequency standard. The frequency of the laser source is locked and the laser beam delivered by the laser source on a transition of an absorber chemical element. The technique combines both operation with saturated absorption and synchronous detection, based on modulating said transition being saturated by the beam passing through the absorber chemical element. This produces a single frequency laser beam whose output frequency is stationary. The frequency is not continuously modulated and is more precise than that which would be obtained operating with single-pass absorption only. The laser source is thus adapted for making a frequency standard.