Development of multi-kW Coherently Combined Fibre Master Oscillator Power Amplifiers

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Development of Yb fibre Master Oscillator Power Amplifiers (MOPAs) is proposed, to enable power scaling from multi-kW to greater than 20 kW in coherently combined laser beam arrays. This aligns with a Leonardo strategic plan to deliver novel and robust laser technology for a range of defense applications. Achieving the highest irradiance on target will be underpinned by the development and demonstration of kW-level fibre MOPAs, at 1m wavelength, with the highest efficiency and tightest control of laser parameters affecting spatial and temporal coherence.State of the art techniques for passive and active phase control under a wide range of environmental conditions will be a key theme of the work, laying the foundations for combining large numbers of fibre MOPAs (N > 10) in an eventual system which is robust against extreme environmental conditions. Further to this, the work will include scope for the development of advanced, phase sensing and adaptive control via the application of neural networks. Packaging of fibre MOPAs is also of importance for optimum amplifier performance and so advanced manufacturing and assembly techniques are proposed, supported by high-power fibre laser modelling and simulation.The project will advance state-of-the-art fibre amplifiers to multi-kW levels of power with the highest efficiency. Novelty is embedded within the project by the application of the latest fibre components, sensing and metrology techniques available within Leonardo and Heriot-Watt University. The amplifiers will exploit the latest advanced packaging methods and one example is the use of glass-to-metal bonding of fibre-collimated beam delivery assemblies, as developed at Heriot Watt University. The proposal includes a new application for neural networks within state-of-the-art coherently combined laser systems.