Frequency stabilization of a GaAs semiconductor laser by use of theoptical-optical double-resonance effect of the Doppler-free spectrum ofRb D1 line

The frequency of a GaAs semiconductor laser was locked to the hyperfine spectrum of the Rb D₁ line by saturation spectroscopy. A first GaAs laser was locked to one of the Doppler-free hyperfine lines using a source modulation method. The burnt hole modulated by the stabilized laser beam was detected by a second laser beam irradicated from the same or the opposite direction and was used as a frequency discriminator to stabilize the second laser. The characteristics of the double-resonance spectrum were measured. The frequency stability of the second laser, which was free from frequency modulation, was estimated to be on the order of 10^-9