New fibres for new lasers - photonic crystal fibre optics for the delivery of high-power light

Lasers are rapidly becoming more useful - they are widely available at shorter wavelengths, emitting shorter pulses and at higher energies and powers than ever before. These characteristics make them especially useful for several industrial applications such as velocimetry, micro-machining and welding, where the beam characteristics delivered to the workpiece are critical in determining the success and efficiency of the process. Unfortunately, the very characteristics that make these laser pulses so useful - their short pulse lengths, low wavelengths and higher energy and power - make them absolutely impossible to deliver using conventional fibre optics. This means that those wishing to exploit the new laser systems would currently have to do so using bulk optics - typically, several mirrors mounted on articulated arms to deliver the pulses to the workpiece.We propose to use an alternative optical fibre technology to solve this problem. Hollow-core fibres which guide light using a photonic bandgap cladding have roughly 1000 times less nonlinear response than conventional fibres, and have far higher damage thresholds as well. In previous work, we concentrated on longer nanosecond pulsed lasers, and demonstrated that we could use these fibres to deliver light capable of machining metals. However, it is with the picoscond and sub-picosecond pulse laser systems now becoming more widespread that the hollow-core fibres really come into their own. For these shorter pulses, transmission through conventional fibres is limited not only by damage, but first by pulse dispersion and optical nonlinear response. These problems can only be surmounted using hollow-core fibre - no competing technology has come even close.Our work programme has several strands, with the common objective being to devise systems capable of delivering picosecond-scale pulses through lengths of a few metres of fibre, at useful energies and powers. To do this, we need to be able to efficiently couple light into the fibres and transmit them, single-mode, over a few metres of fibre with low attenuation. We plan to focus our attention on doing this in the wavelength bands around 1060nm and 530mn, and to investigate the possibility of extending the work to shorter wavelengths. We will work closely with several collaborators from the industrial/commercial sector, ranging from a UK-based supplier of relevant laser systems through to a company developing machining systems and indiustries which actually use such systems. In this way, we plan to provide UK-based industry with a competitive edge on teh global stage, by providing them with access to an academic area where the UK is an acknowledged world leader.

The project delivers on the EPSRC Mission and Vision through the full range of its activities, from high quality applied research and related postgraduate training, advancing knowledge in the broadest sense, providing trained scientists to meet the needs of users and thereby contributing to the economic competitiveness of the UK. It also plans to generate public awareness, communicate research outcomes, and disseminate knowledge, as described. Aside from its considerable academic impact, we aim for our work to have significant impact on the following communities: 1. Commercial advantage for our industrial partners and for the UK economy, through developing and protecting new technology. 2. The physics and photonics community in the UK: this project will help it to remain a vibrant and productive community of researchers. 3. Potential undergraduate and postgraduate students in these areas, who we hope to recruit. 4. Researchers working on the project, who will gain exposure to different ways of working through our exchange programme and who will make contacts in the industrial sector and understand their interests. 5. Researchers and academics in our Universities who are not directly involved in the project, by their access to technologies developed within the project. 6. The reputation of the EPSRC In order to realise our aims, we plan the following actions: a) To work with our industrial collaborators to demonstrate an industrial application, in their laboratories or ours. b) To identify winning directions for the research programme at the half-way stage (between months 18 and 21), reducing diffusion of effort by narrowing down the programme. c) To write at least one feature article in a Trade publication (Laser Focus World, Opto Laser Europe) describing the state-of-the-art in the area and the industrial/commercial relevance of the work. d) To give the project an identifiable presence on the Group web pages. At the end of the first year of the project, we will prepare a video report of the project achievements and plans, linked from the web pages. e) Each institution will offer at least two undergraduate projects of direct relevance to the project during the lifetime of the grant. The project students would work on defined sub-projects, alongside PhD students and postdocs on the project. f) We will run an obligatory inter-institutional exchange programme for students and postdocs, for periods of a week or more at a time, and for several weeks over the life of the project. We will investigate possible exchanges with industrial/commercial partners, particularly in the context of the demonstrator system. g) We will submit a proposal for an exhibit on an aspect of the general topic of lasers in industry to the Royal Society Summer Science exhibition.