The magneto-optic effect is the core part of optical isolators and widely used in optical sensors. The market of optical isolators was estimated to be $0.7B in 2016 and is expected to grow at 5% per annum while that of optical fibre sensors has grown continuously in the last two decades and from $3.38B in 2016 it is expected to reach $5.98B in 2026. To date fiberized devices and sensors based on the magneto optic effect have relied on simple telecom fibres or hybrid solutions with expensive crystals. This project proposes new manufacturing technologies for high performance optical isolators and current/magnetic field sensors aimed to replace the traditional hybrid approach based on crystals with novel glasses/fibres. This approach relies on our recent discovery that slightly-doped Gd-doped glass fibres exhibit a giant magneto-optic coefficient, similar to crystals, yet maintaining low-cost, low loss and high compatibility with fibres. This proposed programme spans from the investigation of giant magneto-optic effect in slightly doped glasses to the manufacture of specialty silica fibres, through the design of fiberized isolators and novel fibre based frequency conversion devices, and their combination in suitable systems for applications in security, industry and medicine. Although the initial effort will relate to the fabrication and characterization of novel glass compositions for glasses and fibres with giant magneto-optic response, the newly developed fibres will then be used to manufacture novel sensors and devices for selected practical industrial implementations in optical isolators and magnetic/current sensing.

Lasers are used for an extremely wide range of manufacturing processes. This is due, in part, to their significant flexibility with respect to parameters such as pulse length, pulse energy, wavelength, and beam size. However, this flexibility comes at a price, namely the significant amount of time that must be dedicated to finding the optimal set of parameters, for each and every manufacturing process or customer specification. The standard practice in industry is the mechanical collection of laser machining data for all parameter combinations, in order to find the optimal combination of parameters. However, this process is both time-consuming and unfocussed, and it can take days or weeks, hence costing unnecessary time and money. Even when the optimal parameters have been determined, small changes, for example in laser power or beam shape, during manufacturing, can result in a final product quality that is below the required standard, once again costing time and money. There will also be instances where the specification is not known in advance due to variability in the manufacturing process. What is needed, therefore, are a series of methodologies for identifying optimal parameters before manufacturing, for providing real-time monitoring and error correction during manufacturing, and for enabling process-control (for example stopping the laser exactly at task completion, or varying the laser power for the final finishing steps). The research field of machine learning has seen some extremely significant developments in recent years, and it is now widely understood to be a catalyst for a fundamental change across almost all manufacturing industries. The objective of this proposal is to develop the technological and human expertise required for the integration of machine learning approaches into the UK laser-based manufacturing industry and the NHS. This proposal therefore seeks to leverage state-of-the-art machine learning techniques for solving well-known problems in laser-based manufacturing and materials processing, resulting in improvements in efficiency, reliability, and precision. The results of this proposal will lead to time and money savings for both the UK laser-based manufacturing industry and the NHS. This proposal will cover the application of neural networks for modelling and optimising of femtosecond laser machining, instantly identifying laser-based manufacturing parameters for any customer specification, automatically compensating for residual cavity effects in fibre lasers, enabling targeted delivery of laser light for psoriasis treatment, and laser welding process enhancement in real-time via multi-sensor data.

Optical fibers are nowadays ubiquitous and exploited in a multitude of applications, from telecommunications to high-power lasers. The last decade has seen the emergence of a new type of optical fiber, the so called multicore (MC) fiber. Unlike traditional fibers, where only a single core is used to carry the light beam, MC fibers are characterized by having a multitude of cores, each one carrying a different light beam. In each core, light can travel in one direction (forward) or in the opposite direction (backward). When forward and backward light beams are simultaneously present, we refer to a counter-propagating configuration. This project aims to study the coupling dynamics between beams of different cores in a counter-propagating configuration, and to demonstrate its application in some important technological areas, ranging from high-power lasers through to telecommunications. Preliminary studies carried out by the team members indicate that when the cores are sufficiently close, then strong coupling induced by the counter-propagating configuration may occur, such that the beams in each core organize themselves in to regular well-defined patterns. For example, the forward beams in each core and exiting the fiber may end up with the same phase irrespective of their initial phase. These results imply natural application in coherent beam combination, which refers to the ability to combine multiple independent light beams so as to obtain a single beam characterized by a high brightness and beam quality at the system output. It is worth noting that here, differently from current state-of-the-art solutions, beam combination is achieved in an "all-optical" way, that is to say without resorting to the use of complex and power-consuming electronic control systems. Indeed it is the beams themselves in each core that self-organize due to their mutual coupling. In this project we will design, fabricate and test bespoke MC fibers where the proposed all-optical beam combination is exploited to build high-power optical sources and novel optical devices for the next generation Internet. Moreover, a general theoretical framework will be developed that will find application not only in optics but also in other important disciplines, such as hydrodynamics. The wide range of skills required for the development of the project will be covered by a multidisciplinary team at the Optoelectronics Research Centre (ORC) of the University of Southampton. The ORC is a world leading academic institution with some of the most advanced laboratories for fiber manufacture and experiments available on the planet.

Dramatic progress has been made in the past few years in the field of photonic technologies, to complement those in electronic technologies which have enabled the vast advances in information processing capability. A plethora of new screen and projection display technologies have been developed, bringing higher resolution, lower power operation and enabling new ways of machine interaction. Advances in biophotonics have led to a large range of low cost products for personal healthcare. Advances in low cost communication technologies to rates now in excess of 10 Gb/s have caused transceiver unit price cost reductions from >$10,000 to less than $100 in a few years, and, in the last two years, large volume use of parallel photonics in computing has come about. Advances in polymers have made possible the formation of not just links but complete optical subsystems fully integrated within circuit boards, so that users can expect to commoditise bespoke photonics technology themselves without having to resort to specialist companies. These advances have set the scene for a major change in commercialisation activity where photonics and electronics will converge in a wide range of systems. Importantly, photonics will become a fundamental underpinning technology for a much greater range of users outside its conventional arena, who will in turn require those skilled in photonics to have a much greater degree of interdisciplinary training. In short, there is a need to educate and train researchers who have skills balanced across the fields of electronic and photonic hardware and software. The applicants are unaware of such capability currently.This Doctoral Training Centre (DTC) proposal therefore seeks to meet this important need, building upon the uniqueness of the Cambridge and UCL research activities that are already focussing on new types of displays based on polymer and holographic projection technology, the application of photonic communications to computing, personal information systems and indeed consumer products (via board-to-board, chip to chip and later on-chip interconnects), the increased use of photonics in industrial processing and manufacture, techniques for the low-cost roll-out of optical fibre to replace the copper network, the substitution of many conventional lighting products with photonic light sources and extensive application of photonics in medical diagnostics and personalised medicine. Many of these activities will increasingly rely on more advanced systems integration, and so the proposed DTC includes experts in computer systems and software. By drawing these complementary activities together, it is proposed to develop an advanced training programme to equip the next generation of very high calibre doctoral students with the required expertise, commercial and business skills and thus provide innovation opportunities for new systems in the future. It should be stressed that the DTC will provide a wide range of methods for learning for students, well beyond that conventionally available, so that they can gain the required skills. In addition to lectures and seminars, for example, there will be bespoke experimental coursework activities, reading clubs, roadmapping activities, secondments to collaborators and business planning courses.Photonics is likely to become much more embedded in other key sectors of the economy, so that the beneficiaries of the DTC are expected to include industries involved in printing, consumer electronics, computing, defence, energy, engineering, security, medicine and indeed systems companies providing information systems for example for financial, retail and medical industries. Such industries will be at the heart of the digital economy, energy, healthcare and nanotechnology fields. As a result, a key feature of the DTC will be a developed awareness in its cohorts of the breadth of opportunity available and a confidence that they can make impact therein.

Standard multi-kW fibre lasers are now considered 'commodity' routinely produced by multiple manufacturers worldwide and are widely used in the most advanced production lines for cutting, welding, 3D printing and marking a myriad of materials from glass to steel. The ability to precisely control the properties of the output laser beam and to focus it on the workpiece makes high-power fibre lasers (HPFLs) indispensable to transform manufacturing through adaptable digital technologies. As we enter the Digital Manufacturing/Industry 4.0 era, new challenges and opportunities for HPFLs are emerging. Modern product life-cycles have never been shorter, requiring increased manufacturing flexibility. With disruptive technologies like additive manufacturing moving into the mainstream, and traditional subtractive techniques requiring new degrees of freedom and accuracy, we expect to move away from fixed, 'fit-for-all' beams to 'on-the-flight' dynamically reconfigurable 'shaped light' with extensive range of beam shapes, shape frequency and sequencing, as well as 3D focus steering. It is also conceivable that the future factory floor will get 'smarter', undergoing a rapid evolution from dedicated static laser stations to robotic flexible/reconfigurable floorplans, which will require 'smart photon delivery' over long distances to the workpiece. Such a disruptive transition requires a new advanced generation of flexible laser tools suitable for the upcoming 4th industrial revolution. Light has four characteristic properties, namely wavelength, polarization, intensity, and phase. In addition, use of optical fibres enables accurate control and shaping in the spatial domain through a variety of well-guided modes. Invariably, all photonic devices function by manipulating some of these properties. Despite their acclaimed success, so far HPFLs are used rather primitively as single-channel, single colour, mostly unpolarised and unshaped, raw power providers and remain at a relatively early stage (stage I) of their potential for massive scalability and functionality. Moreover, further progress in fibre laser power scaling, beam stability and efficiency is hindered by the onset of deleterious nonlinearities. On the other hand, the other unique attributes, such as extended 'colour palette', extensively controllable polarisation and beam shaping on demand, as well as massive 'parallelism' through accurate phase control remain largely unexplored. Use of these characteristics is inherent and comes natural to fibre technology and can add unprecedented functionality to a next generation of 'smart photon engines' and 'smart photon pipes' in a stage II of development. This PG will address the stage II challenges, confront the science and technology roadblocks, seek innovative solutions, and unleash the full potential of HPFLs as advanced manufacturing tools. Our aim is to revolutionise manufacturing by developing the next generation of reconfigurable, scalable, resilient, power efficient, disruptive 'smart' fibre laser tools for the upcoming Digital Manufacturing era. Research for the next generation of manufacturing tools, like in HiPPo PG, that will drive economic growth should start now to make the UK global leaders in agile laser manufacturing - enabling sustainable, resource efficient high-value manufacturing across sectors from aerospace, to food, to medtech devices and automotive. In this way the UK can repatriate manufacturing, rebalance the economy, create high added-value jobs, and promote the green agenda through efficient manufacturing. It will also enhance our defence sovereign capability, as identified by the Prime Minister in the Integrated Review statement to the House of Commons in November 2020.