散弹噪声极限稳定度优于1×10^(-13)τ^(-1/2)的铷频标物理系统

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

近年来,铷原子频标研究取得长足进展,频率稳定度达到10^(-13)τ^(-1/2)量级.为进一步改善铷频标稳定度性能,本文设计了一种高信噪比物理系统.物理系统中的腔泡组件采用微波场磁力线与量子化轴方向高度平行的开槽管式微波腔,滤光泡和吸收泡独立控温.抽运光源采用了光学滤光和同位素滤光双重滤光方案.本文实测了背景光电流I0和鉴频斜率Kd,结果分别为95μA和7.7 nA/Hz,在此基础上计算物理系统的散弹噪声极限稳定度为7.5×10^(-14)τ^(-1/2).研究结果表明,只要锁频环路的电子学噪声得到有效控制,铷频标的频率稳定度突破1×10^(-13)τ^(-1/2),进入10^(-14)τ^(-1/2)量级是完全可能的.

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^(-13)τ^(-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 95μA and 7.7 nA/Hz,respectively,and the calculated limit stability of the shot noise of the physical package was 7.5×10^(-14)τ^(-1/2).The result shows that Rb frequency standard can reach an unprecedented stability level below 1×10^(-13)τ^(-1/2) as long as the electronic system's noise could be well controlled.