Development and magnetometric application of powerful ultraviolet frequency comb lasers

原子磁力计有许多用途，从化学分析、基础物理测试和空间探索，到医疗诊断、导航陀螺仪和矿物的地球物理勘探。在给定的测量时间内，磁力计可以检测到的最弱磁场决定了它的灵敏度，而更高的灵敏度对应用有益。原子磁力计中的原子本质上就像罗盘针。最初将它们全部对准同一方向使磁力计更加灵敏。然而，经过一段时间后，由于环境的影响，它们总是变得不一致。此外，读取罗盘针方向的方式也会影响灵敏度，因为它容易受到外部干扰。最先进的原子磁强计受到权衡的困扰：在稀有气体中通过核自旋获得最长的弛豫时间，而最好的读数方法是直接光学检测。到目前为止，光学探测还不能直接应用于稀有气体中的核自旋，因为没有合适的紫外激光器。松弛时间和读出方法之间的权衡限制了灵敏度。同样，现有的惰性气体原子的初始排列方法，称为超极化方法，由于缺乏直接的光学访问，带来了局限性。本研究计划的重点是开发新型紫外激光器及其在探索稀有气体核自旋磁强计直接光学探测新领域中的物理现象中的应用。长松弛时间和直接光学检测的结合将导致破纪录的磁测灵敏度。该项目的长期目标是突破基础物理的磁强计测试（包括广义相对论的测试和暗物质的搜索）的界限，并使用低场核磁共振光谱法揭示被高磁场掩盖的现象。这种光谱仪也将成为一种易于使用的桌面设备，取代目前用于化学和生化分析的大型、昂贵、使用受限的低温冷却超导体机器。在短期内，该计划将实现三个目标。目标1将开发一种强大的红外激光器，目标2将使用该激光器产生适合于惰性气体核自旋磁强计直接光学检测的紫外激光器。目的三将应用紫外激光研究稀有气体129Xe的直接超极化和磁强计新体制的物理学。

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.