Development and magnetometric application of powerful ultraviolet frequency comb lasers

原子磁强计被用于许多应用，从化学分析、基础物理测试和空间探索，到医疗诊断、导航陀螺仪和矿物地球物理勘探。磁力计在给定的测量时间内可以检测到的最弱磁场定义了其灵敏度，应用程序受益于更高的灵敏度。原子磁力计中的原子本质上就像指南针。最初，将它们全部对齐在同一方向会使磁力计更灵敏。然而，经过一段时间，也就是所谓的松弛时间，它们总是会因为环境的影响而错位。此外，读出指南针方向的方式也会影响灵敏度，因为它容易受到外部干扰。最先进的原子磁力计受到一个取舍的困扰：最长的弛豫时间是在惰性气体中通过核自旋获得的，而最好的读出方法是直接光学检测。到目前为止，由于没有合适的紫外激光，光学探测不能直接应用于惰性气体中的核自旋。弛豫时间和读出方法之间的权衡限制了灵敏度。类似地，现有的惰性气体原子初始对准方法，称为超极化方法，由于缺乏直接光学访问而带来了限制。这项研究的重点是新型紫外激光器的发展及其在惰性气体核自旋磁强计直接光学探测新领域中探索物理现象的应用。长弛豫时间和直接光学探测的结合将导致打破记录的磁测量灵敏度。该计划的长期目标是推动基础物理的磁测量测试(包括广义相对论测试和暗物质搜索)的边界，并使用低场核磁共振光谱分析来发现被高磁场掩盖的现象。这种光谱仪也将成为目前用于化学和生化分析的大型、昂贵、访问受限的基于低温冷却超导体的机器的替代方案。在短期内，该计划将追求三个目标。目的研制一台高功率红外激光器，用于产生适用于稀有气体核自旋磁学中直接光学探测的紫外激光。目的III将利用紫外光激光研究一种新的直接超极化和稀有气体129Xe磁测量的物理机制。

Atomic magnetometers are used in a many applications, ranging from chemical analysis, tests of fundamental physics and space exploration, to medical diagnostics, navigation gyroscopes and geophysical exploration for minerals. The weakest magnetic field a magnetometer can detect in a given measurement time defines its sensitivity, and applications benefit from higher sensitivity. Atoms in atomic magnetometers are essentially like compass needles. Initially aligning them all in the same direction makes the magnetometer more sensitive. However, after some time, called relaxation time, they always become misaligned due to environmental influences. Additionally, the manner in which the direction of the compass needles is read out also influences sensitivity, as it can be susceptible to external interference. State of the art atomic magnetometers are plagued by a trade-off: the longest relaxation times are obtained with nuclear spin in noble gases, while the best readout method is direct optical detection. So far, optical detection could not be directly applied to nuclear spin in noble gases, since a suitable ultraviolet laser was not available. The trade-off between relaxation time and readout method limits sensitivity. Similarly, existing methods for the initial alignment of the noble gas atoms, called hyperpolarization methods, bring about limitations due to the lack of direct optical access. This research program is focused on the development of novel ultraviolet lasers and their use in exploring physical phenomena in a new domain of direct optical detection in noble gas nuclear spin magnetometers. The combination of long relaxation times and direct optical detection will result in record breaking magnetometric sensitivity. The long term goals of this program are to push the boundaries of magnetometric tests of fundamental physics (including tests of general relativity and searches for dark matter) and to use low-field nuclear magnetic resonance spectrometry to uncover phenomena masked by high magnetic fields. This spectrometer would also make an accessible tabletop alternative to the large, expensive, access-restricted cryogenically-cooled-superconductor based machines currently employed for chemical and biochemical analysis. In the short term, this program will pursue three objectives. Objective I will develop a powerful infrared laser, which Objective II will use to generate ultraviolet lasers suitable for direct optical detection in magnetometry with noble gas nuclear spin. Objective III will apply an ultraviolet laser to study the physics of a new regime of direct hyperpolarization and magnetometry with the noble gas 129Xe.