High numerical aperture in multimode microstructured optical fibers.
Microstructured or "air-clad" fibers, with air holes surrounding a large core, have recently demonstrated much wider light-acceptance angles than conventional fibers. An original and accurate method is presented for determining the numerical aperture of such fibers using leaky modes. The dependence on length, wavelength, and various microstructure dimensions are evaluated for the first time for a class of fibers that exhibit exceptionally high numerical apertures. These results show excellent agreement with published measurements on similar fibers and verify that bridge thicknesses much smaller than the wavelength are required for high numerical apertures.
Issa
Nader A
NA
Optical Fibre Technology Centre, Australian Photonics Cooperative Centre, University of Sydney, Australian Technology Park, Eveleigh, New South Wales 1430, Australia. n.issa@oftc.usyd.edu.au