Controllable beating signal using stored light pulseControllable beating signal using stored light pulseControllable beating signal using stored light pulse

We experimentally study the controllable generation of a beating signal using stored light pulses based on electro- magnetically induced transparency （EIT） in a solid medium. The beating signal relies on an asymmetric procedure of light storage and retrieval. After storing the probe pulse into the spin coherence under the EIT condition, two-color control fields with opposite detunings instead of the initial control field are used to scatter the stored spin coherence. The controllable beating signal is generated due to alternative constructive and destructive interferences in the retrieved signal intensities. The beating of the two-color control fields is mapped into the beating of weak probe fields by using atomic spin coherence. This beating signal will be important in precise atomic spectroscopy and fast quantum limited measurements.