Lasers for quantum-enabled position, navigation, and timing technologies

国家基础设施系统依赖于全球导航卫星系统(GNSS)，因此5天的停电将使英国损失50亿英镑。对GNSS在经济上的依赖，例如在电信、电网、供水和物流配送方面，意味着我们越来越需要为定位、导航和授时(PNT)应用寻找可靠和安全的陆基替代方案。量子传感器可以在性能上比传统的PNT传感器提高几个数量级，特别是那些基于超冷原子的传感器，满足目标要求。这些技术包括原子钟和量子惯性传感器，分别提供高灵敏度的时间、加速度和旋转测量，用于量子启用的精确导航和计时。这些基于冷原子的技术的基本组件是超相干激光系统，为一系列原子物种开发，每个原子物种都具有多目标跃迁，需要具有挑战性的低噪声激光性能。例如，在英国国家量子技术传感与定时中心的前两个阶段，我们的团队已经开发出紧凑、窄线宽的可见光半导体激光器，用于中性锶原子的第一和第二阶段冷却，展示了线宽为200赫兹、波长为689 nm的系统，适合应用于伯明翰大学设立的锶光学时钟。在这个项目中，我们将与伦敦帝国理工学院的中心合作研究人员建立新的合作，他们正在开发基于冷原子干涉测量的极其稳定的加速计和陀螺仪。这些传感器与高精度的经典传感器相结合，提供高带宽和短精度与长期精度相结合的组合。这些混合传感器正在开发中，以形成未来量子惯性导航系统的一部分，用于在多个平台上部署，例如英国铁路网；然而，该仪器需要高功率激光来进行原子干涉测量，目前必须依赖于基于商业提供的传统固态激光技术的大型复杂系统，这给易于携带的平台带来了巨大挑战。现在是时候开发一种新颖、紧凑的激光解决方案来在野外演示这些导航系统，利用我们混合半导体激光技术的独特属性来实现创纪录的低相位噪声，并显著降低尺寸、重量和复杂性。在这个博士项目中，我们将设计、开发和应用基于冷原子的惯性传感所需的具有超低相位和频率噪声的新型混合激光系统。这将包括但不限于光学系统设计；激光腔工程，包括电子控制；激光动力学特性，包括强度、频率和相位噪声；新型主动和被动稳定技术的开发；激光光谱学；以及冷原子实验设计。学生还将有机会在帝国理工学院的系统中应用这些激光，为演示量子惯性传感的联合实验做出贡献。

National infrastructure systems are dependent upon the Global Navigation Satellite System (GNSS), such that 5 days of outage would cost the UK >£5bn. This economic reliance on GNSS, e.g. for telecommunications, power grids, water, and logistics distribution, means that we increasingly need to find robust and secure ground-based alternatives for position, navigation, and timing (PNT) applications. Quantum sensors can provide orders of magnitude improvements in performance over classical sensors for PNT, particularly those based on ultra-cold atoms, meeting target requirements. These include atomic clocks and quantum inertial sensors, to provide, respectively, highly sensitive measurements of time, and of acceleration and rotation, for quantum-enabled precision navigation and timing.Essential components of these cold-atom-based technologies are ultra-coherent laser systems, developed for an array of atomic species, each with multiple target transitions that demand challenging, low noise laser performance. For example, within the first two phases of the UK National Quantum Technology Hub for Sensing & Timing our team has developed compact, narrow linewidth visible semiconductor lasers for the first and second stage cooling of neutral strontium atoms, demonstrating systems with <200 Hz linewidth at 689 nm suitable for application in the strontium optical clock set up at the University of Birmingham.For this project we will be establishing a new collaboration with hub co-investigators at Imperial College London who are developing extremely stable accelerometers and gyroscopes based on interferometry of cold rubidium atoms. These are hybridised with high precision classical sensors to deliver combined high bandwidth and shorter precision with long term accuracy. These hybrid sensors are being developed to form part of a future quantum inertial navigation system for deployment on multiple platforms, e.g. the UK rail network; however, the instrument requires high power lasers for the atom interferometry, and currently must rely on a large, complex system based on commercially-supplied conventional solid-state laser technology, imposing significant challenges for easily portable platforms. It is now very timely to develop a novel, compact laser solution to enable the demonstration of these navigation systems in the field, taking advantage of the unique attributes of our hybrid semiconductor laser technology to achieve record low phase noise as well as significant reductions in size, weight and complexity.In this PhD project we will design, develop, and apply novel hybrid laser systems with ultra-low phase and frequency noise, as required for cold-atom-based inertial sensing. This will include, but is not limited to, optical system design; laser cavity engineering, including electronic control; characterisation of laser dynamics including intensity, frequency, and phase noise; development of novel active and passive stabilisation techniques; laser spectroscopy; and cold atom experiment design. The student will also have the opportunity to apply these lasers in the system at Imperial, contributing to joint experiments for demonstration of quantum inertial sensing.