When manufacturing any kind of electronic device, patterning is required to achieve small features, such as different regions of materials with different functions. The ever-increasing complexity of modern electronics and photonics has led to a plethora of approaches to substrate patterning. For each of these approaches, there are always compromises between the speed of patterning (write speed), the minimum feature size, versatility and cost. The most dominant patterning process in electronics and photonics manufacturing is mask-based photolithography. Here, the chip to be patterned is coated with a light-sensitive material known as a "resist," and light is shone onto the resist through a mask with deliberately placed holes. Light that passes through the holes causes a chemical change in the resist, and thus the pattern is transferred from the mask onto the chip. The disadvantage is that each photolithography mask is only suitable for a one particular type of chip design and cannot be reconfigured for the manufacture of other chip designs, and mask design and fabrication is time-consuming and costly. Alternative patterning techniques, known as direct-write lithography, do enable great flexibility in device design, but at the expense of slow patterning speeds, and often large capital and operating costs. Here, we propose a novel process for photolithography, which we name holographic multi-beam interference lithography (HMBIL). HMBIL promises large area patterning with sub-wavelength resolution as well as fast write speeds, short development times, low costs and a dynamically reconfigurable choice of exposure pattern. Using HMBIL, we will demonstrate patterning of arbitrarily-shaped 100 nm feature sizes over large areas with high throughput (>25 cm^2 device area in under 1 hour), which is currently unachievable with direct-write lithography techniques. As a proof-of-principle, we will demonstrate the capability of HMBIL for manufacturing an example device structure: multispectral filter arrays. These filter arrays, when integrated with an image sensor, will allow the acquisition of light spectra for applications as diverse as medical imaging to remote sensing. HMBIL manufacture of multispectral filter arrays will open up a range of avenues for custom detectors and imaging sensors for security, industrial or medical applications. We envisage this versatile new HMBIL process primarily in two locations in the manufacturing chain: Firstly, as a means of rapid prototyping of nanofabricated designs and secondly, as a means of large scale production of individually customised components. This will revolutionise manufacturing processes across a broad range of application areas including miniaturised optoelectronics, versatile point-of-care diagnostic devices, displays and image sensors, on-chip photonics (waveguides and photonic crystals), plasmonics, nano/micro-electromechanical machines, microfluidics, embedded systems and the internet of things, and many more.

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.