Photonic nanowires for optical sensing and signal processing

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Developments in nanotechnology underpin many areas of science and technology. The ability of accurately structure surfaces, materials and devices on the length scale of 1 - 100 nm opens up new device and system possibilities in the areas of ICT, biomedical sensing and environmental monitoring. The program of research outlined in this proposal covers the use of nanofabrication processes based around electron beam lithography and their application to develop high refractive index contrast waveguide structures. There are three areas where student projects will be focused over the next five years, a) electron beam lithography and process development b) photonic wires for wavelength conversion and 3) Photonic wires for optical sensing applications. In 2009 we officially opened our new electron beam lithography system, which allows features down to 10 nm to be defined across large areas. The high beam current, and low stitching errors possible with this tool allow a wide range of structures to be patterned, including nano-structured surfaces for biology, sensing and photonics. The quality of the underlying fabrication processes dictates the quality of the final waveguides, resonators and photonic crystals. We plan to optimize the ebeam patterning process to reduce the minimum feature size, improve writing time and reduce edge roughness that leads to high scattering losses in photonic waveguide structures. The use of high refractive index contrast waveguides to implement wavelength conversion has many advantages. The small core size increases the local intensity, the waveguide structure can be used to dispersion engineering the waveguide to enable phase matching and resonators can be used to further enhance the conversion efficiency. The ability to engineer the dispersion and field profile in a nanowire waveguide also has applications in optical sensing. By narrowing the waveguide, incorporating a photonic crystal, or defect state it is possible to control the overlap of the optical field with the sensing material. The program of research outlined in this application will provide an ideal training ground for students who will gain skills in nanofabrication, integrated optical circuit design and optical testing.