The Compact Laser System for Pulsed Optically Pumped Rubidium Atomic Clock

Abstract

In this paper, we propose an implementation of the compact laser system for POP rubidium atomic clock. The compact system consists of the miniaturized optical platform and the laser driving and control electronic module, and the two parts with the same length and width are stacked together to ensure the output laser beam is exactly incident to rubidium vapor cell in physics package of the clock. (1) The miniaturized optical system adopts integration design milling all the pedestals of optical components on the bottom board of the platform with a volume of 30cm $\\times 17.5$ cm $\\times 5.8$ cm. It mainly includes a DBR diode laser as laser source, AOM as optical switching, sub-Doppler spectroscopy optical path, and optical expansion lens. (2) Laser driving and control electronic module mainly includes the high-precision driving current source, temperature control module, and the lock-in module (including PI and the error signal demodulating module). The temperature of the laser diode is set to $20.1 ^{\\circ }\\mathrm {C}$, with $\\pm 0.001 ^{\\circ }\\mathrm {C}$ fluctuation and the injected current is set around 180.2mA, with ±0.001 mA control precision. The power of output laser is 40mW, with diameter 15mm. With sub-Doppler spectroscopy, the laser has been locked to rubidium transition line (795nm) more than 30 days and relocked within 1 second under unattended laboratory conditions, with power fluctuation less than 0.2% and power stability $5.57 \\times 10^-4$. The experimental results show that the portable compact laser system has strong robustness and reliance, which has an important significance in the engineering process of POP Rb atomic clock.