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In this work we will develop very compact and efficient laser sources with a footprint of just a few square centimetres that are capable of producing more than a billion pulses of light per second, each having a duration of less than one tenth of one trillionth of a second. Such sources have a wide range of applications, including microscopy of biological cells, precise measurement of optical frequencies, spectroscopy and telecommunications, which can all take advantage of both the very short duration of the pulse and its high repetition rate. Many of these applications currently rely on large and relatively inefficient lasers which necessarily limits application design. The miniaturised sources that we propose are based on a waveguide geometry that confines the laser light to very small dimensions, in a similar fashion to that used in glass optical fibres. However, these waveguides are based in crystals such as titanium-doped sapphire and ytterbium-doped tungstate, which have proven themselves capable of providing the very short pulses of light that we are interested in. The waveguide geometry is also capable of supporting components that are integrated into one monolithic device that can both act as the laser gain material necessary to generate the light and provide the ultrafast switching that is required to give short pulses. The waveguides will be fabricated by growing thin layers of doped crystal on undoped substrates, with the dopant providing both the laser gain and the refractive index increase necessary to confine the light to the thin layer. Advanced waveguide structures, based on etching of these layers and re-growth, will be fabricated to give optimum laser performance and allow pumping by high-power diode lasers. The integrated switching components will be based on saturable absorbers that give low loss for high-intensity short optical pulses and high loss for low-intensity continuous wave light. Optimisation of the switching properties of these absorbers and their integration with the waveguide laser will form a major part of this work. We will also investigate the use of the Kerr effect in simple thin-film waveguides to achieve short optical pulse production by using laser resonator designs that take advantage of the fact that the high intensity of the short optical pulses will modify the refractive index such that a focussing effect is achieved. Finally, having developed a number of devices, we will be in a good position to apply them to nonlinear microscopy of biological cells and demonstrate that the high repetition rate of the pulses provides advantages in terms of producing high optical signals without causing damage to the specimens under study.

This proposal falls under the Manufacturing with light call and addresses the area of Pulsed Laser Deposition (PLD) as a route to manufacturing high optical quality, fully single crystal lasing waveguides. PLD is an established technique for deposition of a range of materials, but few so far have used it to grow single crystal structures for application as thin-film lasers. This project is directed at this specific area, and has end goals of high average power (>100W) laser and amplifier operation, from compact (< 1square cm) gain chips, emitting laser wavelengths in the 1-, 2-, and 3- micron region. The second goal is to demonstrate the utility of these devices in "add-on" amplifier modules that can be tailored for commercial lasers systems, to enhance their output performance by an order of magnitude and address high-value laser-based manufacturing applications, including materials processing, the life-sciences and medical areas in particular. Engaging with laser manufacturing companies, the UK Association of Industrial Laser Users, and the EPSRC Centre of Innovative Manufacturing - Laser-based Production Processes at Heriot-Watt University, we will determine an optimum route for capitalisation and knowledge transfer of the fabrication expertise of this novel platform architecture. As a booster project, we will direct our efforts towards maximising the impact of the optimisation processes to create new waveguide gain media that offer unique (and power-scalable) laser performance beyond what is currently available in the industrial laser market place. Coupled with our industrial partners we will test and evaluate the developed amplifier modules for their relevance as potential laser-tools in the manufacturing sector.

Silicon photonics promises to revolutionize modern optoelectronics by allowing for dense integration of components that feature the best optical and electronic functions of the material. In recent years great progress has been made in this area, with many silicon photonic devices now meeting (or exceeding) the performance requirements of state-of-the-art systems. This includes ultra-low loss interconnects as well as high speed optical regenerators, amplifiers, modulators, and detectors, which form the building blocks for photonic circuits. However, to date, much of this progress has been achieved on silicon-on-insulator (SOI) platforms with a thick buried oxide layer, which are largely incompatible with electronic device development, and relatively expensive, thus precluding truly integrated systems from reaching the high-volume market. Consequently, there are still crucial challenges to overcome before the performance benefits of SOI photonics outweigh the costs and design constraints, leaving the door open for alternative platforms to be considered. In this programme we propose to develop a low cost and low temperature laser materials processing procedure to fabricate high quality polycrystalline semiconductor photonic platforms that will rival the performance of their SOI counterparts. Laser processed polycrystalline materials are already well-established for use in electronic technologies where some performance can be sacrificed in favour of reduced processing costs, for example, in the backplanes of smart phones and televisions. However, if the polycrystalline grains can be grown as large as the individual components, then the optical (and electronic) properties will approach those of the single crystal materials. By building on the platform established by the electronics community, this work seeks to grow large grain polycrystalline materials to realize low loss photonic components. Importantly, the high localization of this laser crystallization procedure directly alleviates issues associated with multi-material and multi-layer photonic device integration, and can also be used to modify or repair the individual components at a late stage in the fabrication, helping to increase the production yield and reduce the costs of integrated systems. Furthermore, this method offers the unique advantage of removing the substrate dependence from semiconductor photonics, thus offering the possibility to extend the application space through the use of substrate materials with enhanced optical functionality, increased transparencies, or even flexible plastics. By reducing costs and barriers associated with device fabrication, our innovative project will set the scene for wide spread use of laser-engineered semiconductor photonic components in mainstream optoelectronic systems.

We will train cohorts of graduates from different scientific backgrounds together in a unique interdisciplinary programme that combines physical sciences, computer sciences and biomedicine and breaks down the boundaries between these disciplines. They will apply this interdisciplinary training to develop underpinning new physical science research to address three key UK healthcare challenges: - Rebuilding the ageing and diseased body - Understanding cardiovascular disease - Improving trauma and emergency medicine The research programme will be underpinned by a multi-disciplinary taught programme and enhanced by transferable and project management skills training, as well as Knowledge Transfer and Public Engagement of Science activities. The CDT builds on our four years experience of CDT training of physical scientists at the biomedical interface and harnesses the existing and dynamic research community of excellent physical scientists, distinguished for their ability to and commitment to research at the life science interface, together with a team of leading biomedical scientists and clinicians, with whom there are already established collaborations. This new CDT represents an evolution in our activities and new biomedical foci, while retaining the expertise, ethos and track record of promoting a change in culture at the Physical Science / Biomedicine interface, and of nurturing the next generation of researchers to develop the skills and experience required to explore new physical sciences for biology and healthcare, without the perceived cultural and language barriers. The CDT addresses an identified need from our industrial partners for PhD scientists trained at the interface with biology and medicine, and able to communicate and research across these disciplines, such that they are flexible and innovative workers who can move between projects and indeed disciplines as company priorities evolve and change. This need is reflected in the involvement in and commitment to our bid from our industrial partners. They will co-fund students, offer placements and site-visits, deliver lectures as part of the training and monitor and advise on the training programme. The programme will also benefit from public sector involvement including the Diamond Light Source, local hospitals and Thinktank Science Museum.