Modulation transfer spectroscopy for frequency stabilization of 852 nm DBR diode lasers

We report on the realization of modulation transfer spectroscopy on the D₂ transition of ¹³³Cs for frequency stabilization of the 852 nm distributed Bragg reflector diode lasers. Proper modulation frequency, optimal pump and probe beam power are investigated according to the peak-to-peak amplitude and the slope of the modulation transfer spectroscopy signals. The laser frequency can be locked robustly for more than one day. The beat signal between two independent lasers has a frequency drift of 716 kHz at 5000 s. The result shows that the fractional frequency instability of the locked laser falls below 5 × 10^-11 at 1000 s averaging time.