Rubidium-beam microwave clock pumped by distributed feedback diode lasers

A rubidium-beam microwave clock, optically pumped by a distributed feedback diode laser, is experimentally investigated. The clock is composed of a physical package, optical systems, and electric servo loops. The physical package realizes the microwave interrogation of a rubidium-atomic beam. The optical systems, equipped with two 780-nm distributed feedback laser diodes, yield light for pumping and detecting. The servo loops control the frequency of a local oscillator with respect to the microwave spectrum. With the experimental systems, the microwave spectrum, which has an amplitude of 4 nA and a line width of 700 Hz, is obtained. Preliminary tests show that the clock short-term frequency stability is 7×10^-11 at 1 s, and 3×10^-12 at 1000 s. These experimental results demonstrate the feasibility of the scheme for a manufactured clock.