A Chip-Scale 2-Photon Rubidium Atomic Clock

我们的愿景是提供一个芯片级的双光子Rb光学原子钟，频率参考和低相位噪声振荡器相结合的窄线宽激光器，使用III-V增益芯片与氮化硅外部光栅锁定到集成Rb MEMS单元和下变频到10 GHz的输出信号，使用氮化硅微频率梳驱动的III-V脉冲，锁模激光器。一个氮化硅光子集成电路（PIC）平台将用于异构集成的所有光子和MEMS真空组件所需的定时系统。一个类比是哈里森的怀表，H4，1773年获得经度奖，因为它的小尺寸减少了海军舰艇上温度和加速度漂移的不确定性。通过与文献的比较和包络线后的计算，我们估计性能为100 fs/（Hz^0.5）和1 fs精度的物理封装尺寸约为40 x 30 x 5 mm的时钟。这对应于在Blackett审查关键国家基础设施的72小时保持期要求之后的2 ns的不确定性。对于仅定时误差占主导的位置不确定性，这导致位置不确定性< 1 m。我们的目标是提供一个性能与Microchip MHM-2020有源氢脉泽相当的时钟，但体积小10，000倍，质量低250倍，功耗低150倍。活性氢脉泽在7天的测量时间内比铯原子钟稳定100倍，在1天内比商业CSAC（芯片级原子钟）精确100，000倍。

Our vision is to deliver a chip-scale two-photon Rb optical atomic clock, frequency reference and low phase-noise oscillator by combining narrow linewidth lasers using III-V gain chips with silicon nitride external gratings locked to integrated Rb MEMS cells and down-converted to a 10 GHz output signal using a silicon nitride microring frequency comb driven by a III-V pulsed, mode-locked laser. A silicon nitride photonic integrated circuit (PIC) platform will be used for the heterogeneous integrated of all the photonic and MEMS vacuum components required for the timing systems. An analogy is Harrison's pocket watch, H4, that won the Longitude Prize in 1773 as the small size reduced the uncertainties from temperature and acceleration drifts on navy ships.Through comparison with the literature and back of the envelope calculations we estimate a performance of 100 fs/(Hz^0.5) and 1 fs accuracy for the proposed clock with a physics package of around 40 x 30 x 5 mm in size. This corresponds to an uncertainty of 2 ns after the Blackett review 72 hour hold-over period requirement for critical national infrastructure. For a position uncertainty where only timing errors dominate, this results in a position uncertainty < 1 m. Our aim is for a clock with comparable performance to a Microchip MHM-2020 Active Hydrogen Maser but x10,000 smaller, x250 lower mass and x150 lower power. Active hydrogen masers are 100 times more stable than Cs atomic clocks at measuring times of 7 days and x100,000 more accurate at 1 day than a commercial CSAC (Chip Scale Atomic Clock).