High-reflectivity surface-relief gratings in single-mode optical fibres

The design, fabrication and experimental characterisation of surface-relief gratings in single-mode optical fibres are described. Novel structures employing high-refractive-index over-layers are discussed with which reflectivities up to 98% and linewidths down to 0.8 nm at the first-order Bragg wavelength have been achieved. Applications of these structures are described.