PHOTONIC BAND GAP FIBRES: THE NEW WAY OF GUIDING LIGHT

Photonic Bandgap Fibres (PBGFs) are a radically new class of optical fibres whose guiding properties rely on the existence of photonic bandgaps. These fibres can guide light within an air-core thanks to a periodic array of micrometer-size holes running along the fibre length [1], see Fig 1a,b. PBGF have opened up numerous possibilities in photonics, largely through their ability to overcome the limitations of conventional optical fibres, for example by permitting guidance of light at wavelengths where silica fibres present high loss. They offer great prospects for communications due to the potential for low loss that results from the light being guided in air. In addition, these features make them ideal for sensors since there can be a large overlap between the light and gases, liquids, or nanoparticles introduced into the central hole. Such fibres could then be used wherever high sensitivity detectors are needed such as in the bio-medical field, or even for homeland security applications. PBGFs are fabricated by stacking and fusing arrays of glass capillaries into a tube of 2-3 centimetres diameter which is then drawn at high temperatures to fibre form. This approach allows the complex preform structure to be scaled down to the size of a human hair, see Fig. 1b. By appropriately designing the stacked preform, the air holes within the PBGF can have a wide range of shapes and sizes in highly controlled microgeometries. By tuning the geometrical properties of the holes, the optical properties of the fibre can be engineered; here at the ORC we have demonstrated the fabrication of complex structures with incredible precision, Fig 1b,c