Metal-glass nanocomposites through nanoengineering to application.

For many centuries the presence of metal nanoparticles has been evident because of the unusual colour effects associated with them. The red and yellow colours of many medieval church windows originated from silver, gold and copper nanoparticles embedded in the window glass. The first evidence of using gold nanoparticles in antiquity dates back to the 4th century AD (The Lycurgus Cup). The physics of the processes remained a mystery until Michael Faraday, the well-known 19th century physicist, discovered that this effect is due to a new type of optical absorption in metal particles with dimensions substantially less than the wavelength of light. Metal particles which have sizes of the order of one to several hundreds of nanometres, are the subject of intensive research efforts across the world. This is due to the fascinating differences in the optical properties they exhibit compared to bulk metals. When a metal nanoparticle is smaller than the wavelength of light, the light reflected from it is replaced by light scattering, which is particularly strong at the resonance frequencies of collective electron excitations in the nanoparticle. These oscillations are known as particle plasmons or surface plasmon resonances. For noble and alkali metals, where the conduction electrons are sufficiently free-electron-like, the collective excitations show themselves as pronounced resonance effects in optical scattering and absorption spectra. Recent advances in nanotechnology have made it possible to create artificial nanostructured composite materials whose optical properties are determined by their structure, rather than by the characteristics of their constituents. These optical properties are distinctly different from those of conventional composites. Such nanocomposites are often referred to as metamaterials. The most established way to manufacture metamaterials for photonics applications is by engineering the optical response of large groups of repeated submicron patterns, lithographically formed from metal films, using rigorous grating theory for the description of the optical properties of a given pattern. Here, I propose the development of metamaterials that - in the spirit of the original meaning of this term - are based on nanostructured composite materials and exhibit exceptional properties due to the inclusion of artificially implanted inhomogeneities. This concept is based on tailoring the properties of, and providing new functionalities to, artificial materials created by controllable formation of metal nanoparticles in glass matrices; so-called metal-glass nanocomposites (MGNs).I will systematically investigate the entire range of parameters necessary to develop metamaterials by exploiting the generic functionalities of patterned MGNs. These artificial nanomaterials will be designed and investigated in detail utilising a combination of a novel fabrication techniques, and by modifying/tailoring their optical properties with short and ultra-short laser pulses. The technology developed will find a wide range of applications not only in optics and optical industries via optical amplifying, switching and polarisation control, but also in micro- and optoelectronics - e.g. the integration of optical and electronic components at extremely small scales for optical computing. Given the broad application potential for these materials it would be possible to optimise the outcomes and generate internationally competitive output in several key areas of science and technology. A number of manufacturers and industries will ultimately benefit from the work - e.g. computer chip industries, manufacturers of optical data storage devices for security applications, optical sensing devices, display technology, healthcare devices and artists/manufacturers of contemporary jewellery. I believe that the proposed programme will address key problems in this field and will contribute to the UK's leading position in this area of research.

This research is primarily motivated by a desire to access new applications in photonics and optoelectronics, results of which may lead to the integration of optical and electronic components at extremely small scales for optical computing. I believe that in addition to computer chip industries a number of other manufacturers will ultimately benefit from the work (e.g., manufacturers of optical data storage devices for security applications, optical sensing devices, display etc). The proposal also includes interfacing with the arts and design. The work centres around the effects which can be generated by implanting metal ions into glasses, causing these ions to cluster and aggregate into nanoparticles with controlled particle size and density gradient and then to manipulate the distribution, shape and orientation of these metal inclusions in up to 3-dimensions. Suitable design and accuracy of control allows 3-D metallic structures within the host substrate to be implemented and together with the resulting effective refractive index distributions this, in principle, allows a range of optoelectrical features to be available for many applications. The general subject area has been extensively studied at different levels for sometime now and has always been driven by the prospect of the exciting final applications that may be enabled. The present proposal is firmly based on specific knowledge and skills the applicant has developed in two separate areas but which can be combined to advance progress in this field. These relate to the use of a unique technique to introduce ions into glasses at much higher densities than currently possible with older techniques, and the use of annealing coupled with lasers of various pulse durations to move the ions and clusters into desired shapes and spatial configurations. These results will facilitate production, due to novel functionality, of a variety of cheaper and more effective devices for optical and photonics applications, and thus have a strong impact on a number of sectors such as photonics, materials science, etc. Hence, my work bridges the remits of two research areas, namely nanomaterials physics/science and laser micro/nano engineering, through design to application. The results to be expected will considerably increase our knowledge of new processes and metamaterials for optoelectronics. The anticipated technical impacts of the project, which should contribute towards the goal of the research, will be media and techniques for fabrication of metamaterials, which are cheaper to process at a higher level of complexity and wider functionality, metamaterials functioning at elevated/optical frequencies that are now too difficult and expensive to access, and novel ultra-fast and effective modulators, switches and optical amplifiers/sources based on these metamaterials. The necessary steps to ensure that these impacts flow from the project are dissemination of the results in a wide range of appropriate scientific/engineering journals and international conferences, demonstration of new technology and their application, transferring developed technology and approaches to industry via KTP TSB projects, and utilising preferences of the metamaterials and techniques in developing a wider family of optoelectronic devices using the advanced functionality of the designed nanomaterials. New technology represents real progress beyond the state-of-the-art and offers an excellent and time limited opportunity for the UK to enhance and extend its lead in the range of optoelectronics devices ultimately implemented globally. The research lines proposed will also provide an excellent basis for the training of research students in areas demanding skills in optoelectronics, laser micro/nano processing and materials science.