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

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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.