The modern society's need for fast and reliable communications supports the operation of industries, the Internet of things, transportation systems, entertainment electronics and allows the exchange of information and knowledge. Most services rely on optical interconnects that provide low-cost, high-capacity, low-power consumption network connections, including data centers, satellites, supercomputers, and the Internet. According to the Cisco report, the network traffic, including the Internet, has increased to 40 Zettabytes of data in 2020. To put the numbers in perspective, the total data generated from the beginning of humanity until 2003 is 0.5% of a Zettabyte. Furthermore, the ever-increasing data traffic accounted for 12% of total global emissions in 2020. As a result, it is crucial to develop efficient networks with higher capacity and reduced power consumption. This project will contribute to more efficient modulators, which will impact communication systems used in ground and satellites to increase capacity, reduce pollution, and improve the environmental sustainability of optical interconnects in aerospace systems, data centers, high-performance computers, and networks. This research will exploit the properties of indium arsenide quantum dots, including 1. the radiation and temperature resilience to demonstrate a modulator for aerospace applications: indium arsenide quantum dot's radiation and temperature tolerance will outperform competing developments employing quantum wells, which 1. tolerates 10x and 5x orders of magnitude less radiation and temperature, 2. offers less bandwidth, and 3. high power consumption mainly when operating at high temperatures. This modulator will contribute to substitute current solutions, where heavy, power-hungry, and slow electrical interconnects by light, low-power consumption, and ultra-fast optical interconnects. The research will leverage 1. high-data rates satellite communications underpinning improved services, including fast Internet in remote and rural areas, and 2. the reduced size and weight will improve spacecraft fuel consumption and pollution towards net-zero emission. 2. the resilience to threading dislocation, and material stress of quantum dots, will be exploited to grow the modulator over silicon to bring more efficient modulators to the silicon photonic platform. Due to the weak modulating effects in silicon, it is not possible to produce efficient modulators. On the other hand, quantum dots exhibit stronger effects than silicon leveraging more efficient modulators and will outperform current quantum well monolithic integration approaches due to their resilience when grown over silicon. This development will impact the commercial optical interconnects using silicon-based photonic integrated circuits (PICs) and current networks relying on them. By integrating the quantum dot modulator into the existing commercial silicon-based PICs, the performance of ground optical interconnects will be improved, underpinning more efficient networks in data centers, high-performance computers, and the Internet. VTT, a silicon photonic foundry, will provide the silicon PICs. To ensure commercial relevance of the research, this project partners with key industrial players in the aerospace and data/telecom sectors and includes Airbus, ALTER Technology, Bay Photonics, STAR-Dundee and VTT. Additionally, the work will be carried out at the National Epitaxy Facility and the Institute for Compound Semiconductors. Hence, this project is well placed on training researchers in relevant industrial problems, evaluating the technology's commercial relevance, and guiding future developments.

In a consortium led by Heriot-Watt with St Andrews, Glasgow, Strathclyde, Edinburgh, Dundee, Huddersfield and NPL, the "EPSRC CDT in Use-Inspired Photonic Sensing and Metrology" responds to the focus area of "Meeting a User-Need and/or Supporting Civic Priorities" and aligns to EPSRC's Frontiers in Engineering & Technology priority and its aim to produce "tools and technologies that form the foundation of future UK prosperity". Our theme recognises the key role that photonic sensing and metrology has in addressing 21st century challenges in transport (LiDAR), energy (wind-turbine monitoring), manufacturing (precision measurement), medicine (disease sensors), agri-food (spectroscopy), security (chemical sensing) and net-zero (hydrocarbon and H2 metrology). Building on the success of our earlier centres, the addition of NPL and Huddersfield to our team reflects their international leadership in optical metrology and creates a consortium whose REF standing, UKRI income and industrial connectivity makes us uniquely able to deliver this CDT. Photonics contributes £15.2bn annually to the UK economy and employs 80,000 people--equal to automotive production and 3x more than pharmaceutical manufacturing. By 2035, more than 60% of the UK economy will rely on photonics to stay competitive. UK companies addressing the photonic sensing and metrology market are therefore vital to our economy but are threatened by a lack of doctoral-level researchers with a breadth of knowledge and understanding of photonic sensing and metrology, coupled with high-level business, management and communication skills. By ensuring a supply of these individuals, our CDT will consolidate the UK industrial knowledge base, driving this high-growth, export-led sector whose products and services have far-reaching impacts on our society. The proposed CDT will train 55 students. These will comprise at least 40 EngD students, characterised by a research project originated by a company and hosted on their site. A complementary stream of up to 15 PhD students will pursue industrially relevant research in university labs, with more flexibility and technical risk than in an EngD project. In preparing this bid, we invited companies to indicate their support, resulting in £5.5M cash commitments for 102 new students, considerably exceeding our target of 55 students, and highlighting industry's appetite for a CDT in photonic sensing and metrology. Our request to EPSRC for £6.13M will support 35 students, with the remaining students funded by industrial (£2.43M) and university (£1.02M) cash contributions, translating to an exceptional 56% cash leverage of studentship costs. The university partners provide 166 named supervisors, giving the flexibility to identify the most appropriate expertise for industry-led EngD projects. These academics' links to >120 named companies also ensure that the networks exist to co-create university-led PhD projects with industry partners. Our team combines established researchers with considerable supervisory experience (>50 full professors) with many dynamic early-career researchers, including a number of prestigious research fellowship holders. A 9-month frontloaded residential phase in St Andrews and Edinburgh will ensure the cohort gels strongly, equipping students with the knowledge and skills they need before starting their research projects. These core taught courses, augmented with electives from the other universities, will total 120 credits and will be supplemented by accredited MBA courses and training in outreach, IP, communication skills, RRI, EDI, sustainability and trusted-research. Collectively, these training episodes will bring students back to Heriot-Watt a few times each year, consolidating their intra- and inter-cohort networks. Governance will follow our current model, with a mixed academic-industry Management Committee and an International Advisory Committee of world-leading experts.

The Photonic Integrated Circuit Packaging ACademy (PICPAC) project shall create and deliver course content and materials on packaging necessary to enable the rapidly growing field of photonics within the semiconductor sector. Semiconductor based photonics devices are critical in enabling telecommunications, datacomms, imaging, and quantum technologies (e.g. quantum computing, quantum cryptography and quantum sensing). However, to operate in real world applications, delicate semiconductor chips must be packaged to interface with the outside world. Aspects of photonic packaging that must be considered are the mechanical, electrical, thermal and photonic interfaces as well as the interplay between the different aspects. While there has been much recent investment in foundry activities (upstream semiconductor activity) there has been little investment in downstream activities (assembly, packaging and testing - APT) and their is a clear gap in practical knowledge in the area of APT within the UK semiconductor landscape. The PICPAC project aims to create a national centre for semiconductor photonic packaging training located within the nationally recognized South West semiconductor cluster. Bay Photonics (BP) and Davies & Bell (DB) will capture industrial training requirements and create course content together with South Devon College (SDC) who will deliver the courses in a variety of formats. The format of the courses will be flexible and the timing will be flexible (effectively, on demand), to align with the needs of industry. Once created, this will be the only programme of its kind in the country.

Optical fibre systems that can generate, amplify or manipulate light signals across a broad range of wavelengths and powers are highly desired for applications spanning optical communications to quantum processing and sensing. Although conventional silica glass fibres are routinely used in applications to transport signals in the 400-2000 nm spectral region, their high losses in the mid-infrared wavelength region (>2000 nm) excludes their use in emerging areas such as environmental monitoring, weather-resilient free-space communications, absorption spectroscopy, and quantum sensing. Additionally, the capabilities of silica fibres to manipulate the signals (e.g., modulate, convert, switch, regenerate) are limited. This is because optical signal processing relies on the ability to alter the transmission properties of the fibre by the presence of high power (nonlinear) light, and the nonlinear coefficient of silica is low. Although the low nonlinearity of silica can be overcome to some extent by using long fibre lengths (hundreds of metres) and/or high-power control beams (kilowatts), the resulting systems are typically bulky and expensive. This project aims to address these key limitations to extend the application of nonlinear fibre systems by using a new class of fibre where the silica core has been replaced by a crystalline silicon material. Compared to traditional all-silica glass fibres, the silicon core offers a significantly higher nonlinear coefficient (> 100 times) and an extended transmission window covering much of the near to mid-infrared spectral regions (1200-8000 nm). By developing methods to reduce the losses, optimise the nonlinear conversion efficiency and robustly connect the silicon core fibres to commercially available glass fibre components (conventional silica fibres up to 2000 nm, and hollow core fibres or fluoride fibres for longer wavelengths), nonlinear systems can be constructed that support operation over a range of powers and signal wavelengths, as required by many practical applications. Within the project, we aim to design and test the all-fibre connected silicon fibre systems for high performance and ease of use across various applications within the areas of optical communications and quantum technologies. For example, we will design devices that can triple the amplification bandwidth of telecom signals compared to existing technologies, thus enabling transmission of three times more data over the same optical fibre. We will use the extended transparency of the core to generate mid-infrared signals that can be used in high performance free-space data transmission, even in adverse weather conditions such as fog or rain. And finally, we will exploit the low losses and extended spectral coverage of the interconnected silicon fibres to produce alignment-free sources of quantum states of light for applications reaching beyond traditional quantum information systems and into exciting areas such as daylight satellite-to-ground secure communication, enhanced sensing through fog or smoke, and squeezed-state metrology in the mid-infrared. As well as opening up new avenues of exploration for nonlinear fibre systems, we expect this work will also help to increase the wide-spread adoption of silicon fibres within diverse research groups and photonic industries seeking robust, compact and flexible systems.

Silicon photonics is the manipulation of light (photons) in silicon-based substrates, analogous to electronics, which is the manipulation of electrons. The development cycle of a silicon photonics device consists of three stages: design, fabrication, and characterisation. Whilst design and characterisation can readily be done by research groups around the country, the fabrication of silicon photonics devices, circuits and systems requires large scale investments and capital equipment such as cleanrooms, lithography, etching equipment etc. Based at the Universities of Southampton and Glasgow, CORNERSTONE 2.5 will provide world-leading fabrication capability to silicon photonics researchers and the wider science community. Whilst silicon photonics is the focus of CORNERSTONE 2.5, it will also support other technologies that utilise similar fabrication processes, such as MEMS or microfluidics, and the integration of light sources with silicon photonics integrated circuits, as well as supporting any research area that requires high-resolution lithography. The new specialised capabilities available to researchers to support emerging applications in silicon photonics are: 1) quantum photonics based on silicon-on-insulator (SOI) wafers; 2) programmable photonics; 3) all-silicon photodetection; 4) high efficiency grating couplers for low energy, power sensitive systems; 5) enhanced sensing platforms; and 6) light source integration to the silicon nitride platform. Access will be facilitated via a multi-project-wafer (MPW) mechanism whereby multiple users' designs will be fabricated in parallel on the same wafer. This is enabled by the 8" wafer-scale processing capability centred around a deep-UV projection lithography scanner installed at the University of Southampton. The value of CORNERSTONE 2.5 to researchers who wish to use it is enhanced by a network of supporting companies, each providing significant expertise and added value to users. Supporting companies include process-design-kit (PDK) software specialists (Luceda Photonics), reticle suppliers (Compugraphics, Photronics), packaging facilities (Tyndall National Institute, Bay Photonics, Alter Technologies), a mass production silicon photonics foundry (CompoundTek), an epitaxy partner for germanium-on-silicon growth (IQE), fabrication processing support (Oxford Instruments), an MPW broker (EUROPRACTICE), a III-V die supplier (Sivers Semiconductors) and promotion and outreach partners (Photonics Leadership Group, EPIC, CSA Catapult, CPI, Anchored In). Access to the new capabilities will be free-of-charge to UK academics in months 13-18 of the project, and 75% subsidised by the grant in months 19-24. During the 2-year project, we will also canvas UK demand for the capability to continue to operate as an EPSRC National Research Facility, and if so, to establish a Statement of Need.