MCLAREN: Miniaturised Cold Atom Gravimeter for Space Applications

本项目的总体目标是开发一个小型重力仪演示器，测试重力仪小型子系统的空间兼容性，并制定空间部署的发展路线图。在项目期间，将设计和开发关键子系统，以满足SWaP要求，或者提供实现SWaP要求的明确途径。解决当前冷原子传感器设计的局限性不仅将确定一条通往太空的道路，而且将克服在更直接的地面重力测量市场中采用的障碍，并通常确定一条使冷原子传感器的商业野心成为现实的道路。该项目将输出紧凑和空间兼容的子系统，可以形成早期的收入来源，包括空间兼容的驱动电子设备，信号发生器，真空系统，光纤网络，光学架构和波长计。从圣安德鲁斯大学的具体观点来看，我们在这个项目中的一部分是利用光的干涉作为提案的一个关键方面。由于光的波动性，光的干涉是一种普遍存在的现象。特别是，光在无序介质中的传播会经历反复的散射和干涉，产生一种被称为散斑的“颗粒状”图案。这被认为是一个随机化过程，它破坏了包含在初始光束中的信息，对许多光学系统是有害的。事实上，许多工程师研究斑点，以消除其影响。然而，有趣的是，最近越来越多的人认识到-包括圣安德鲁斯的关键观察-这种复杂的模式富含关于入射激光源和环境的有用信息，具有惊人的潜在用途。St Andrewsteam的目的是使用激光散斑并将其应用于新形式的测量和分析，这将有利于重力仪我们的目的是证明散斑图案可以用来确定光源的波长。使用这样的散斑图案的优点是，它们是复杂的，因此可以体现在一个非常小的足迹信息，提供了一个出发点，可以取代传统的方法，波长确定使用一维光栅和色散的原则。此外，该方案通过使用这些斑点图案来电子反馈以控制和稳定激光系统的输出，从而避免了对气室的需要。我们要强调的是，非常低的噪声和锁定激光系统对于操作和实现许多冷原子技术至关重要。特别是对于重力仪，将冷却和拉曼激光器锁定在亚飞秒分辨率将产生显著的精度进步，将其与适合于空间应用的坚固性和紧凑性的系统相结合，使得基于全反射的锁定方法成为空间应用的理想子系统，并且代表了该领域的一个步骤变化。

The overall aim of the present project will be to develop a compact gravimeter demonstrator, test the gravimeters compactsubsystems for space compatibility and establish a development roadmap for space deployment. During the project criticalsubsystems will be designed and developed that will address SWaP requirements either during the project, or provide aclear path to their attainment.Addressing the limitations of current cold atom sensor designs will not only identify a route to space readiness butovercome barriers to adoption in the more immediate terrestrial gravimetry markets, and in general identify a route to makethe commercial ambitions of cold atom sensors realisable. This project will output compact and space compatiblesubsystems that can form early revenue streams including space compatible drive electronics, signal generators,miniaturised vacuum systems, fibre networks, optical architectures and wavemeters.From the specific viewpoint of the University of St Andrews, our part of this project is to exploit the interference of light for akey aspect of the proposal. The interference of light is an ubiquitous phenomenon due to its wave nature. In particular, lightpropagating in a disordered medium undergoes repeated scattering and interference, creating a "grainy" pattern known asspeckle. This is regarded as a randomization process which destroys information contained within the initial beam and isdeleterious to many optical systems. Indeed many engineers study speckle to remove its effect. Intriguingly however thereis recently growing recognition - including key observations by St Andrews - that this complex pattern is rich in usefulinformation on both the incident laser source and the environment, with startling potential uses. The aim of the St Andrewsteam is to use laser speckle and apply it to new forms of measurement and analysis that would benefit the gravimeterWe aim to demonstrate that the speckle patterns can be used to determine the wavelength of the light source. Theadvantages of using such speckle patterns are that they are complex, and can therefore embody information in a verysmall footprint, offering a departure which can supersede traditional methods for wavelength determination which use onedimensional gratings and principles of dispersion. Furthermore, this scheme obviates the need for gas cells by using thesespeckle patterns to feedback electronically to control and stabilise the output of a laser system. We would stress that verylow noise and locked laser systems are essential to operate and enable numerous cold atom technologies. In particular fora gravimeter, locking the cooling and Raman lasers at subfemtometer resolution will yield significant advances in accuracy.Coupling this with a system that is suited to ruggedisation and compactness for space based applications makes all-fibrespeckle based locking methods ideal subsystems for space based applications, and represents a step change for the field.