基于Bragg衍射的大动量反冲原子干涉重力仪研究

High precision atom interferometry gravimeters have been wildly used in precision measurements, test of fundamental physics and geophysics. It is significant to further improve the resolution of atomic gravimeter to fulfill the requirements of many scientific experiments. One efficient way for improving the sensitivity could be realized experimentally by increasing the interferometry signal. Based on our former atomic gravimeter, we propose to use high order Bragg diffraction to transfer multi-photons momentum to the atoms, which will dramatically increase the interferometry time-space area, and then increase the gravity induced interferometry phase shifts. And finally the resolution will be improved as the interference signal is increased by large momentum transfer. During the whole Bragg atom interferometry process, atoms stay in one internal state, which makes this kind of interferometer has the advantage of non-sensitive to the electromagnetic field. We are expected to improve an atom interferometry gravimeter's resolution to 1×10^-9g/Hz^1/2 level using Bragg diffraction technology, by research on high power Bragg laser beam, well controlling of the atom momentum state and increasing the fringe contrast.

高精度冷原子干涉重力仪被广泛应用于精密测量物理、基本物理规律检验以及地球物理等研究领域，进一步提高原子重力仪的测量分辨率具有重要的研究意义。实验上可以通过增加干涉相移信号来提高原子干涉重力仪的分辨率水平。本项目拟在课题组前期铷原子干涉重力测量研究的基础上，采用基于高阶Bragg衍射的大动量反冲技术，使原子获得高于双光子的多光子反冲动量，增加原子干涉仪的时空面积，增大干涉相移，从而提高原子重力仪的测量分辨率。此外，在由Bragg衍射脉冲主导的干涉过程中，原子都处于单一内态，所以降低了环境电磁场噪声对该类型原子干涉仪的影响。本课题拟通过对高功率Bragg激光束的产生、Bragg脉冲对原子动量态的操控、干涉条纹对比度的提高等关键技术攻关，期望将原子干涉重力仪分辨率突破到1×10^-9g/Hz^1/2水平，为相关基础和应用研究打好基础。

高精度冷原子干涉仪被广泛应用于物理常数测量、惯性传感、地球物理等研究领域。在这些科学研究中，进一步提高原子重力仪的测量分辨率具有重要的研究意义。本项目采用基于Bragg衍射的大动量反冲技术，设计并实现了基于Bragg衍射的原子干涉重力仪，完成了项目的主要研究内容，基本达到了预期指标。本项目的主要工作概括如下：完成了一套由1560 nm到780 nm的高功率、低相噪激光倍频系统，并用其制备了高功率Bragg光和Raman光；实现了原子的Bragg衍射，最高转移8光子动量，获取了基于Bragg衍射的原子干涉条纹；实验表明该Bragg型原子干涉重力仪的测量灵敏度达到1.9×10-8g/Hz1/2，积分1000 s后分辨率达到7×10-10g，比同类型的Bragg干涉重力仪灵敏度提高了近3倍。

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