Pulsed optically pumped rubidium clock with ultrahigh resonance contrast

In this paper, we report a dispersive detection technique with ultrahigh resonance contrast based on magneto-optical effect. To demonstrate specifically the advantages of the dispersive detection, we applied it in the pulsed optically pumped (POP) clock to obtain the clock signal. The contrast of Ramsey central fringe versus the parameters of pumping light, detection light and microwave power are studied experimentally. An ultrahigh resonance contrast greater than 90% is obtained. The frequency stability of POP clock in terms of Allan deviation for dispersive detection is improved by an order of magnitude over the absorptive detection under equivalent condition. We also present the preliminary experimental result in case of off resonance detection where a laser with large frequency detuning is used as detection light. The signal intensity detected by off resonance light is improved about 70% than the resonant light.