Development of a pulsed optically pumped 87rb vapor cell clock

Abstract

The atomic clock using a vapor cell is appropriate for many applications because it has simple, compact, and stable characteristics. The atomic clock is realized by the use of the atomic transitions between the ground state hyperfine levels. The two approaches have been used to implement a vapor cell atomic clock. One is the microwave-optical double resonance (MODR) technique and the other is the coherent population trapping (CPT) technique. We propose a pulsed optically pumped $(POP)^{87}$Rb atomic clock using a laser absorption in MODR technique and a carrier mode suppression of a phase modulated beam using an optical cavity in CPT technique. We report an optical detection approach instead of the detection of a microwave decay method in a $(POP)^{87}$Rb vapor cell atomic clock for its compact setup. We present the data processing method which transfors the optical transmission signal into the clock transition signal in the optical detection approach. We obtained the FWHM of the clock transition signal which is 293 Hz by this data processing method when the microwave interrogation time $t_{m}$ is 3 ms and microwave power is -4 dBm. The line broadening of the clock transition signal versus the microwave interrogation time for the respective microwave optimum power was measured. In order to estimate the tolerance of the temperature variation of the temperature stabilization servo, we measured the fractional frequency stability versus temperature variation which is $6.6\times10^{-10} / \degC$. The measured frequency stability of our $(POP)^{87}Rb atomic clock was $2 \times10^{-11}$ $\tau_{\frac{-1}{2}}$ and the short-term stability could be improved by employing the more stable laser system and the more precise data processing method. And to enhance the long-term stability, the temperature variations of the laser diode and the components of the electronic systems should be greatly reduced. We adopted an electro-optic modulator (EOM) approach to produce a phas...