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In recent years, it has been found that the irradiation of optical materials by intense, very short (femtosecond) laser pulses causes permanent modifications that might be utilised to create a host of new photonic components for applications to many different fields. Whilst several laboratories worldwide have examined aspects of this process, and have identified new phenomena, many with very small feature sizes, very much less than 1 micron, their nature and properties are poorly understood. Despite all of the excitement in this technology, only a small number of attempts have been made to harness and exploit the concept to create new devices, and much careful experimentation is required to make this happen. The basic types of device that can be envisaged might be formed in many different materials, and the transparent glasses, silica, and polymers are particularly important, since they can be used to create relatively complex written structures in which light may be trapped (waveguided) and used to perform communication, sensing, or measurement functions. The entire technological process has many features in common with better-established UV light inscription processes for waveguides and gratings, which are of extreme importance in modern photonic technology, but the femtosecond inscription mechanisms have many potential advantages and new features that have not been explored, particularly within the UK. It is possible, then, that an entirely new production technique can emerge, offering devices that outperform existing ones, and offer many new and exciting features. In particular, these devices would exploit the ability to produce structures buried anywhere in the volume of the material, with very small (nano-scale) feature sizes. The idea of fully 3-dimensional integrated optics causes much excitement, and has proven to be very difficult to achieve by any alternative technological method over 2 decades. This programme seeks to investigate these processes building upon extremely exciting first results in our laboratories. The goals of the programme lie in learning to harness the complicated processes in order to produce new fibre optic and planar photonic device structures. Numerous fields of activity can benefit from this, but we have chosen to target the majority, though not all, of our studies towards devices that have much-needed uses in biomedical and surgical areas. Amongst these we include smart or steerable catheters and endoscopes, wherein the fibre optic systems are rendered directionally sensitive using novel, tiny sensing structures produced by the femtosecond technique. Similar structures can be used in the control of microsurgical tools for minimally-invasive surgery. And, there is a wealth of non-medical uses for directionally sensitive fibre devices. In the planar format, the inscription technique can provide similar sensing functions with applications in the biological or life sciences, providing new tiny forms of what has come to be called the lab-on-a-chip . The prospect to modify structures with such tiny dimensional scales leads to new sensing and measurement phenomena that can aid many biomaterials and pharmaceutical studies. And the prospect of realising high density stacked optical structures within the volume of the material sample leads to a massive increase in the functional density and compactness of photonic devices. Behind all of this lie many new and little studied or understood physical phenomena: a proper understanding of these, and control over their properties and reproducibility, will be a significant achievement and can stimulate new businesses in many areas of application.
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