Cladding-mode-resonances in air-silica microstructure optical fibers

We present a comprehensive study of mode propagation in a range of differen t air-silica microstructured fibers. The inscription of both Bragg and long -period gratings (LPGs into the photosensitive core region of microstructur ed air-silica fibers has allowed us to generate complex transmission spectr a from a range of fibers with various fill fractions and with increasing ai r-clad hole diameters, The spectral characteristics for typical air-hole ge ometry's are explained qualitatively and modeled using beam propagation sim ulations, where the numerical modeling corroborates the experimental measur ements. Specifically, the data reveal the propagation of higher order leaky modes in fibers with periodically spaced air-holes, and relatively small a ir-fill fraction, And as the air-hole diameter increases, spectra show clad ding modes defined solely by the inner air-clad region. We describe these m easurements and corresponding simulations and discuss their implications fo r the understanding of such air-hole structures.