Fiber laser system for Rb atomic fountain clock

Abstract

A compact and robust all-fiber laser system comprising fiber-optical components for a Rb atomic fountain clock is demonstrated. The laser sources were based on the frequency doubling of two seed lasers at a wavelength of 1560 nm, which were locked using digital frequency locking and modulation transfer spectroscopy. During the Sisyphus cooling period, the PZT control voltage of the fiber laser was ramped to detune the laser frequency to 170 MHz, and we get an atomic temperature of 1.9 □K. A series of customized optical fiber splitters, acousto-optic modulators (AOMs), and shutters were integrated into two 2U enclosures as cooling and repumping light modules. The entire laser system was integrated into a 22U cabinet and was characterized via polarization, power, and frequency stability measurements over 100 days. Apply the laser system to the Rb atomic fountain clock, which exhibited a frequency stability of less than 4.5 × 10^-16 at the interval of 24 h.