There are very few exponential trends in technology that stay exponential for long. Moore's law is probably the best example, where an exponential (the doubling of the number of transistors in modern microprocessors every 18-24 months) has persisted for almost four decades, with great benefit to modern society. On the other hand, in recent years, there has been another slightly more worrying exponential. This is the total amount of data that we as a society have been consuming. It has been growing exponentially for the past decade and shows no signs of slowing down. It is probably best illustrated by modern data centers that have grown in size scale and number all around the globe to the point where by 2030, they are expected to consume ~ 20% of the world's total electricity supply and even today, they emit more CO2 than the global airline industry. If you look at a data center more carefully, most of the energy is dissipated not in computing, but in sending bits around at very high data rates over variable distances, and this is predominantly done in the optical domain. If we can build a more efficient photonic integrated circuit for handling this optical communication, we can address this energy problem in principle. The work done as part of this project is aimed towards developing the underlying platform and a scalable manufacturing process for building these efficient photonic devices. Our approach is to apply the best manufacturing processes (derived from silicon photonics and silicon MEMS foundries) to the best available optical materials (compound semiconductors). We believe this is a natural route towards building the most energy efficient integrated photonic devices. In addition to data center transceivers, the platform developed here will also be applicable to other areas ranging from photonic devices for satellite communication to cryogenic photonics platforms for quantum information.

Photonics has moved from a niche industry to being embedded in the majority of deployed systems, spanning sensing, biomedical devices and advanced manufacturing, through communications, ranging from chip-to-chip and wireless access to transcontinental scale, to display technologies, bringing higher resolution, lower energy operation and new ways of human-machine interaction. Its combination with electronics enables the Digital Future. The Government's UK Semiconductor Strategy and UK Wireless Infrastructure Strategy both recognise the need for highly trained people to lead developments in these technology areas, the Semiconductor Strategy referring explicitly to the role of CDTs in filling the current shortage of highly trained researchers. Our proposed CDT has been designed to meet this need. Currently manufactured systems are realised by combining separately developed photonics, electronic and wireless components. This approach is labour intensive and requires many electrical interconnects as well as optical alignment on the micron scale. Devices are optimised separately and then brought together to meet systems specifications. Such an approach, although it has delivered remarkable results, not least the communications systems upon which the internet and our Digital Future depends, limits the benefits that could come from systems-led co-design and the development of technologies for seamless integration of photonics, electronics and wireless. Our proposed CDT aims to provide multi-disciplinary training enabling researchers to create the optimally integrated, energy efficient, systems of the future. To realise such integrated systems requires researchers who have not only deep understanding of their specialist area, but also an excellent understanding across this interdisciplinary area ranging across the fields of photonics, electronics and wireless, hardware and software. We aim to meet this important need by building upon the uniqueness and extent of the Cambridge and UCL research programmes, where activities range across materials for future systems; higher levels of electronic, photonic and wireless integration; the convergence of wireless and optical communication systems; combined quantum and classical communication systems; the application of THz and optical low-latency connections in data centres; techniques for high capacity access networks; the substitution of many conventional illumination products with photonic light sources and extensive application of photonics in medical diagnostics and personalised medicine. Future systems will increasingly rely on more advanced systems integration, and so the CDT supervisor team includes experts in electronic circuits, wireless systems and enabling 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 technical expertise, RRI, ES, commercial and business skills to enable the > £24 billion annual turnover UK electronics and photonics manufacturing industry to create the optimised, closely integrated systems of the future. The PES CDT will provide a wide range of learning methods for research students, well beyond that conventionally available, so that they can gain the required skills. In addition to conventional lectures and seminars, for example, there will be bespoke experimental coursework activities, educational retreats, reading clubs, road-mapping activities, RRI and ES studies, secondments to companies and other research laboratories and business and entrepreneurship courses. Students trained by the CDT will be equipped to expand the range of applications into which these technologies are deployed in key sectors of the Digital Futures and wider economy, such as communications, industrial manufacturing, consumer electronics, data processing, defence, energy, engineering, security and medicine.

Cloud storage is rapidly growing because we all, as individuals, companies, organisations and governments, rely on data farms filled with large numbers of 'server' computers using hard disk drives (HDDs) to store personal and societal digital information. One server is required for every 600 smartphones or 120 tablet computers, and trends such as Industry 4.0 and the Internet of Things are generating yet more new data, so the Cloud will continue to grow rapidly. The Cloud accounted for 25% of storage in 2010 and will account for >60% by 2020. As a result of these trends, the Cloud storage market is growing at 30% p.a. and is expected to be worth nearly $100b by 2022. While almost all personal computing and related electronic devices have migrated to solid state drives (SSD), HDDs are the only viable technology for cloud storage and a step change in the capacity of HDDs is required. Due to the limitations of existing magnetic materials, a new technology is needed to increase the density of magnetic data recording beyond the current 1Tb/sq. inch out to well beyond 10Tb/sq. inch and meet the 30% annual growth rate. Heat assisted magnetic recording (HAMR) has been identified to overcome physical challenges and has now demonstrated proof of principle. HAMR requires the integration of photonic components including lasers, waveguides and plasmonic antennas within the current magnetic recording head transducer. With a total addressable market (TAM) of 400-600 million hard disk drives p.a. with 3-4 heads per drive, HAMR is projected to require 2+ billion diode lasers p.a. & become the largest single market for laser diodes and photonic integration. HAMR will only be successful if it can be deployed as a low-cost manufacturable technology. Its successful development will therefore drive low-cost photonic integration and plasmonic technology into other industries and applications. Queen's University Belfast & University of Glasgow co-created CDT PIADS in 2014/15 with 9 companies, and the founding vision of CDT PIADS was to train cohorts of high calibre doctoral research students in the skillsets needed by the data storage & photonics partner-base & the wider UK supply chain. Students are trained in an interdisciplinary environment encompassing five themes of robust semiconductor lasers, planar lightwave circuits, advanced characterisation, plasmonic devices, & materials for high density magnetic storage. By providing high-level scientific & engineering research skills in the challenges of integrating photonics & advanced materials alongside rich & enhanced skills training, graduating doctoral students are equipped to lead & operate at the highest technical levels in cross geographic distributed environments. In renewal we exploit the opportunity to engage & enhance our programme in collaboration with Science Foundation Ireland & the Irish Photonics Integration Centre with complementary capabilities including packaging & microtransfer printing for materials/device integration. Our training is expanded to include research on computational properties of functional & plasmonic materials and introduce a new programme of professional externally validated leadership training & offering both PhD and EngD routes. All 50 students recruited in renewal will have industry involvement in their programme, whether through direct sponsorship/collaboration or via placements. Our anchor tenant partner, Seagate Technology, has a major R&D and manufacturing site in the UK. Their need to manufacture of up to 1b p.a. photonic integrated devices at this site gives CDT PIADS a unique opportunity to create an ecosystem for training & research in photonic integration and data storage. The anchor tenant model will bring other companies together who also need the human resource & outcomes of the CDT to meet their skills demands.

The sensing, processing and transport of information is at the heart of modern life, as can be seen from the ubiquity of smart-phone usage on any street. From our interactions with the people who design, build and use the systems that make this possible, we have created a programme to make possible the first data interconnects, switches and sensors that use lasers monolithically integrated on silicon, offering the potential to transform Information and Communication Technology (ICT) by changing fundamentally the way in which data is sensed, transferred between and processed on silicon chips. The work builds on our demonstration of the first successful telecommunications wavelength lasers directly integrated on silicon substrates. The QUDOS Programme will enable the monolithic integration of all required optical functions on silicon and will have a similar transformative effect on ICT to that which the creation of silicon integrated electronic circuits had on electronics. This will come about through removing the need to assemble individual components, enabling vastly increased scale and functionality at greatly reduced cost.

This proposal seeks funding to create a Centre for Doctoral Training (CDT) in Connected Electronic and Photonic Systems (CEPS). Photonics has moved from a niche industry to being embedded in the majority of deployed systems, ranging from sensing, biophotonics and advanced manufacturing, through communications from the chip-to-chip to transcontinental scale, to display technologies, bringing higher resolution, lower power operation and enabling new ways of human-machine interaction. These advances have set the scene for a major change in commercialisation activity where electronics photonics and wireless converge in a wide range of information, sensing, communications, manufacturing and personal healthcare systems. Currently manufactured systems are realised by combining separately developed photonics, electronic and wireless components. This approach is labour intensive and requires many electrical interconnects as well as optical alignment on the micron scale. Devices are optimised separately and then brought together to meet systems specifications. Such an approach, although it has delivered remarkable results, not least the communications systems upon which the internet depends, limits the benefits that could come from systems-led design and the development of technologies for seamless integration of electronic photonics and wireless systems. To realise such connected systems requires researchers who have not only deep understanding of their specialist area, but also an excellent understanding across the fields of electronic photonics and wireless hardware and software. This proposal seeks to meet this important need, building upon the uniqueness and extent of the UCL and Cambridge research, where research activities are already focussing on higher levels of electronic, photonic and wireless integration; the convergence of wireless and optical communication systems; combined quantum and classical communication systems; the application of THz and optical low-latency connections in data centres; 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 CDT includes experts in electronic circuits, wireless systems and software. By drawing these complementary activities together, and building upon initial work towards this goal carried out within our previously funded CDT in Integrated Photonic and Electronic Systems, it is proposed to develop an advanced training programme to equip the next generation of very high calibre doctoral students with the required technical expertise, responsible innovation (RI), commercial and business skills to enable the £90 billion annual turnover UK electronics and photonics industry to create the closely integrated systems of the future. The CEPS CDT will provide a wide range of methods for learning for research students, well beyond that conventionally available, so that they can gain the required skills. In addition to conventional lectures and seminars, for example, there will be bespoke experimental coursework activities, reading clubs, roadmapping activities, responsible innovation (RI) studies, secondments to companies and other research laboratories and business planning courses. Connecting electronic and photonic systems is likely to expand the range of applications into which these technologies are deployed in other key sectors of the economy, such as industrial manufacturing, consumer electronics, data processing, defence, energy, engineering, security and medicine. As a result, a key feature of the CDT will be a developed awareness in its student cohorts of the breadth of opportunity available and the confidence that they can make strong impact thereon.