A Physics Package with Shot-noise Limited Frequency Stability Better Than 1×10-13τ-1/2 for Rubidium Atomic Frequency Standards

Abstract

The performance of the rubidium (Rb) atomic frequency standard has achieved significant improvement in recent years. Its frequency stability has already reached the order of 10-13τ-1/2. To further improve Rb frequency standard's stability performance, we developed a high signal-to-noise ratio (SNR) physics package whose cavity-cell assembly consists of a slotted-tube microwave cavity, separated filter and absorption cells. The microwave cavity has a homogenous field distribution along the quantization axis, and the filter and absorption cells are temperature-controlled independently. We also used an optical and isotopic filtering scheme to suppress shot noise from the pumping light. The physics package's final background photocurrent I0 and the frequency discrimination slope Kdwere measured to be 95 μA and 7.7 nA/Hz, respectively, and the calculated limit stability of the shot noise of the physical package was 7.5×10-14τ-1/2. The result shows that Rb frequency standard can reach an unprecedented stability level below 1×10-13τ-1/2 as long as the electronic system's noise could be well controlled.

Keywords

• rubidium atomic frequency standards
• physics package
• slotted-tube cavity
• shot noise
• frequency stability