Laser power stabilization for the detection of the populations of the atomic double levels in Cs fountain clock

In this paper we present experimental results on the laser power stabilization of the detection system in Cs fountain clock. In order to stabilize the laser power, we have constructed a feedback loop by using an acousto-optic modulator, a photodetector, and a servo controller. The control-loop can make the relative intensity noise of the laser beam reduce from 1.33×10^-4 Hz^-1/2 to 7.16×10^-6 Hz^-1/2 at 2 Hz. However, if the beam used in the control-loop is obtained by using PBS, the two detection beams in fountain clock cannot be stabilized at the same time. Therefore, we propose a new scheme by using a piece of uncoated optical glass plate as a splitter to obtain the branch beam used in the control-loop. Experimental results demonstrate that the power stabilities of the two detection beams are both at 10^-5 level (based on rms value) for 1.5 hours at the same time.