Frequency Stabilization of a Semiconductor Laser under Direct Frequency Shift Keying Using the Saturated Absorption Signal

The oscillating frequency of a semiconductor laser was stabilized at the Rb-D 2 absorption line under direct frequency shift keying (FSK). The control system equipped with a peak-hold circuit provided the frequency stability of 10 -9 >σ(2, τ)>10 -12 at the averaging time 0.05 s<τ<40 s when the Doppler-limited absorption line was used as a frequency reference. This stability was better than that obtained by the traditional control system without the peak-hold circuit under direct FSK. Using the saturated absorption signal, the frequency stability was improved more than one order of magnitude in comparison with that obtained using the Doppler-limited absorption signal.