Advanced fibre designs for high power laser beam delivery and generation

Microstructured optical fiber (MOF) technology provides a powerful means to develop fibers with unique and enabling properties with potential uses spanning a very wide range of applications. Microstructuring of the fiber material allows access to properties unobtainable in the bulk. These include (a) the possibility to guide light in air (through photonic band-gap or low density of state effects) including spectral regions where the bulk is opaque; (b) single mode guidance over extended spectral ranges (referred to as endlessly single mode (ESM) guidance); (c) extended control of dispersion and (d) the fabrication of fibers with very much larger values of numerical aperture (NA) than possible using conventional fiber fabrication approaches. Furthermore these unique properties may be tailored to enhance wavelength generation in fibers through non-linear effects or in fibers containing rare-earth dopants. The paper discusses recent progress in the design and fabrication of such fibers that exploit several of these opportunities.