"This project aims to inscribe novel gratings, including fibre Bragg gratings and long period fibre gratings, within air-core photonic bandgap fibres (PBFs) and to systematically investigate their applications within optical communications, fibre lasers and sensors. If successful the project will open the door to a host of new grating-based devices. This project will address the fundamental problem of how to induce a periodic index modulation that can be experienced by an optical mode propagating within an air core – a problem that has seriously obstructed the development of gratings and grating-based devices in air-core PBFs for the past decade. I propose to investigate several promising techniques for perturbing/deforming periodically the air holes along the fibre axis with either a CO2 laser, or a femtosecond laser. In addition, I shall develop a special air-core PBF with a photosensitive core wall that should allow grating inscription using the common UV laser exposure technique. Air-core PBF gratings are quite distinct from any former gratings in index-guiding fibres and have unique optical properties due to the air core. Moreover, the unique microstructure in air-core PBFs will allow thermo- or electro-optic polymers and other advanced materials to be incorporated into the air holes/core, offering a new platform for developing innovative communication and sensing devices. Active and passive devices such as in-fibre polarisers, tunable filters, and pulse compressors could be used to develop next generation all-optical fibre communication networks. The smart sensing elements to be developed, especially gas, biochemical, and biophotonic sensors, could be used to monitor environmental pollution, gas concentration, water quality, and the health of railways, bridges, building, and mines. Such applications will greatly promote communication, laser and sensing technologies and should lead to significant economic and societal benefits to Europe."