The recording of high resolution spectral images and non-invasive monitoring of wall paintings in grotto sites, tombs and buildings are particularly important since these paintings are extremely vulnerable. The remoteness of some of the sites, the inaccessible height of some of the paintings and the difficulty in controlling the environment they are in, all contribute to their vulnerability. Imaging of wall paintings at high resolution currently requires either scaffolding or some heavy and cumbersome mechanical structure to lift the camera to the upper parts of a wall or ceiling. The aim of the proposed project is to develop a portable imaging system that is light-weight and flexible for in situ high resolution, accurate colour and spectral imaging in the visible/near infrared (400-1000nm) and short-wave infrared (900nm-1700nm), including fluorescence imaging of wall paintings and other large paintings from ground level. The system would provide the means of non-invasive monitoring of the conditions of the paintings, revealing past intervention, studying painting techniques and identifying pigments and disseminating the 3D colour images to the general public. The portability of the system means that it can be taken to remote sites to image paintings in situ without the need for scaffolding or other cumbersome mechanical structures and that it can also be used to image large museum paintings and painted objects in situ at high resolution.

Thin film coatings are core components within the majority of the technology that surrounds us, typically providing optical, electronic and/or protective/decorative functionality. Thin films are a key enabling technology within numerous vital sectors, including optical devices, telecommunications, energy and energy storage, functional/durable materials, biomedical, etc. Many commercial applications have helped drive the development of thin film coatings. For example, ion beam deposition (IBD) was originally developed for fabricating multilayer reflectors for laser ring gyroscopes, and then later exploited within the telecoms industry. The precision and uniformity of these coatings enabled the telecoms industry in the 1970s to fabricate DWDM (dense wavelength division multiplexing) filters, allowing transmission (and subsequent separation) of multiple optical signals at nearby wavelengths. Although IBD has typically remained the method of choice for the most demanding optical applications, the cost associated with the technology means that UK companies have to source from overseas companies. We note that the UK has a large number of companies that procure high-performance IBD coatings, within sectors such as defence, biomedical, laser engineering, and quantum technology. We also note that the UK plays a leading role in a number of large European and international science projects, which require enhanced performance IBD coating technology, including ELI (Extreme Light Infrastructure) and in gravitational wave detection (LIGO and the Einstein Telescope). The University of Strathclyde has pioneered electron cyclotron resonance (ECR) ion beam deposition, which can surpass the performance of current state-of-the-art ion beam deposition. This technology also has the ability to reduce associated costs, due to having core components which are maintenance-free (unlike current RF ion beam deposition). This project seeks to transfer this technology to a leading international supplier of photonic and optoelectronic devices, to enable the UK to be the international go-to-supplier of extreme performance optical coatings for next generation optical and quantum technologies.

Thin film coatings are core components within the majority of the technology that surrounds us, typically providing optical, electronic and/or protective/decorative functionality. Thin films are a key enabling technology within numerous vital sectors, including optical devices, telecommunications, energy and energy storage, functional/durable materials, biomedical, etc. Many commercial applications have helped drive the development of thin film coatings. For example, ion beam deposition (IBD) was originally developed for fabricating multilayer reflectors for laser ring gyroscopes, and then later exploited within the telecoms industry. The precision and uniformity of these coatings enabled the telecoms industry in the 1970s to fabricate DWDM (dense wavelength division multiplexing) filters, allowing transmission (and subsequent separation) of multiple optical signals at nearby wavelengths. Although IBD has typically remained the method of choice for the most demanding optical applications, the cost associated with the technology means that UK companies have to source from overseas companies. We note that the UK has a large number of companies that procure high-performance IBD coatings, within sectors such as defence, biomedical, laser engineering, and quantum technology. We also note that the UK plays a leading role in a number of large European and international science projects, which require enhanced performance IBD coating technology, including ELI (Extreme Light Infrastructure) and in gravitational wave detection (LIGO and the Einstein Telescope). The University of Strathclyde has pioneered electron cyclotron resonance (ECR) ion beam deposition, which can surpass the performance of current state-of-the-art ion beam deposition. This technology also has the ability to reduce associated costs, due to having core components which are maintenance-free (unlike current RF ion beam deposition). This project seeks to transfer this technology to a leading international supplier of photonic and optoelectronic devices, to enable the UK to be the international go-to-supplier of extreme performance optical coatings for next generation optical and quantum technologies.

Some of the most exciting experiments planned in the UK and internationally - from studying extreme light-matter interactions, to the exploitation of quantum technologies - are demanding unpreceded performance in mirror coating technology. Optical thin film coatings appear ubiquitously in the technology around us, however current available performances will not meet the requirements for, and will thus limit the exploitation from, many of these experiments. For example, emerging extreme light-matter experiments are now handling power densities an order of magnitude higher than those previously achieved. This includes major UK infrastructures, including the Central Laser Facility (CLF) and the Scottish Centre for the Application of Plasma-based Accelerators (SCAPA), in addition to partnership initiatives in Europe including the 850MEuro European funded Extreme Light Infrastructure (ELI). All these experiments will soon require laser damage threshold (LDT) performance in the highly reflective mirrors at a level not currently available. This proposal, for the first time, will seek to exploit advanced optical coating technologies, developed with the field of gravitational wave astronomy, for use in intense-light matter experiments. Moreover, the capabilities developed will significantly support existing activities within the Quantum Technologies for Fundamental Physics (QTFP) and the UK's continued effort in gravitational wave astronomy.

Scientific examination of works of art is essential for conservation, preservation and understanding of material change. Ideally non-invasive methods of examination need to be used. Optical Coherence Tomography (OCT) is a non-invasive, non-contact imaging technique designed for in vivo imaging of the eye and other biological tissues. OCT is a fast scanning Michelson interferometer capable of 3D imaging of subsurface microstructure. In 2004, the principal investigator led a collaboration pioneering the application of OCT to paintings. In the same year, two other groups also reported OCT examination of jade, ceramics and paintings. Apart from the non-invasive examination of the stratigraphy of paint and varnish layers, OCT has also been shown to be the most sensitive technique for revealing preparatory underdrawings beneath paint layers owing to its high dynamic range and depth selection capabilities. OCT has been used for dynamic monitoring of the wetting and drying of different varnishes, varnish removal using solvents, real time laser ablation of varnish layers and tracking of canvas deformation due to environmental changes. OCT has found application in the examination of ancient glass, enamel, ceramics, jade, faience and parchment. Our current research has shown that OCT has the potential to become a routine non-invasive tool in museums allowing cross-section imaging anywhere on an intact object where there are no other methods of obtaining subsurface information. OCT can go beyond qualitative imaging toward quantitative measurement of optical properties giving information on ageing processes and assisting material identification.\n\nWhile current OCTs have shown potential in this field, they are optimised for biomedical applications. Some major limitations are: (i) lower depth resolution compared to conventional microscopic examination of paint cross-sections; (ii) limited probing depth through highly scattering paint. A depth resolution of less than ~4 microns is needed to resolve the thinnest varnish and paint layers, and the operation wavelength needs to be longer to increase the penetration depth. The depth resolution of OCT is proportional to the source bandwidth. OCT research in recent years has moved towards development of novel wideband sources. \n\nOCT systems for biomedical applications are generally restricted to wavelengths between 800nm and 1300nm for the best compromise between water absorption and tissue scattering. However, the requirements of art conservation are very different; our recent survey of the transparency of historical artists' pigments has shown that a third of pigments in oil have >5 times improvement in transparency at wavelnegth of 2000nm compared with 900nm. Few OCT systems have been built beyond 1300 nm. The best resolution commercial OCT at any wavelength is around 6 microns. We propose to explore OCT systems at higher resolutions and at 2000nm wavelength using novel superfluorescent fibre sources, pushing the boundaries of OCT to match the information content given by the microscopic examination of sample cross-sections currently employed. This project intends to explore new problems in conservation and art history that the next generation OCT for art can help to solve and push the boundaries in near infrared OCT imaging for non-biological material. It will significantly improve the capabilities of OCT through increasing the depth resolution and penetration in order to reduce the need for sampling and enable the subsurface microstructure to be imaged on intact objects where sampling is not possible, encourage more frequent and thorough examination of the whole object for early warning of deterioration, improve the visibility and resolution of underdrawing for art historical research, better inform conservation strategy and create long term savings in the cost of conservation, and hence firmly establish OCT as a tool for non-invasive imaging in the heritage field.