Replacement Laser for Holographic Fabrication of Photonic Crystals

This grant proposal is intended to enable us to buy a replacement for a laser system. The laser has been troublesome in the past and is getting worse - it has been unusable for two months, and in that time the manufacturer has not been able to suggest how it might be returned to use. The laser is essential to our research - without a replacement we cannot continue with a project already funded by EPSRC which is described below.Photonic crystals are optical materials with regular, repeated, wavelength-scale microstructure. Photonic crystals are 'optical semiconductors' whose properties make them uniquely suitable for the fabrication of photonic integrated circuits. Their characteristic property is a 'photonic band gap' - a forbidden frequency range within which the structure acts as an optical insulator. 'Doping' with structural defects introduces localized electromagnetic modes which may be engineered to create the components of integrated optical devices, such as waveguides and microcavities. The high level of optical isolation that may be achieved within a photonic crystal means that photonic crystal-based integrated optical circuits promise to approach the density of integration of electronic devices, a development which will revolutionize the handling of telecommunications signals. In a collaboration between the Physics and Chemistry Departments at Oxford University we have developed a completely new way to make photonic crystals. We use a three-dimensional holographic laser interference pattern to create the necessary sub-wavelength microstructure in a thick film of photoresist. We then use a purpose-built confocal microscope to modify the structure to create waveguide etc. structures within it. This technique is inherently cheap and quick / it gives uniquely flexible access to a wide range of 3D photonic crystal phenomena and could be readily scaled up to commercial manufacture. In this proposal we aim to create 3D photonic crystals which are suitable for use in the range of wavelengths used in optical fibre telecommunications. We also aim to create engineered structural defects within 3D photonic crystals and to investigate the relationship between the structure of the defects and the optical properties of the 'doped' crystal as an important step towards three-dimensional integration of micrometer-scale optical devices.