Nonlinear optics in periodic media

Summary form only given. Periodic media such as fibre Bragg gratings are finding increasing use in a wide range of telecommunications equipment due to their design flexibility. By adding an additional periodicity to a waveguide or bulk crystal it is possible to significantly alter its optical properties over a narrow wavelength range. Perhaps the most well known example is the creation of a photonic band gap in fibre Bragg gratings which leads to high reflectivity and strong dispersion over a narrow wavelength range. Crucially the wavelength range over which light is reflected is determined by the periodicity and hence gratings can be designed to reflect light at any predetermined wavelength. At our research centre we are currently looking at nonlinear optics in a wide range of periodic materials ranging from microstructured optical fibres to two dimensionally poled nonlinear materials and Bragg gratings.