Combining the idea of metamaterial fibers developed at the University of Sydney, with recent work on modal selectivity in gold-nanowire enhanced optical fibers  performed at IPHT Jena, we have shown that large-area hollow core fibers with sub-wavelength gold nanowires in the cladding can exhibit peculiar properties. In particular, by changing the filling fraction of metal, we can vary which mode has the lowest loss. Interestingly, some of the modes have much lower losses than equivalent modes in fibers made with the individual constituent materials. Furthermore, simple scattering matrix parameter retrieval techniques give an adequate description of the modal losses, which simplifies the design procedure. This was shown at an example CO2 laser wavelength, but is applicable at other wavelengths.

For the full paper, see: A. Tuniz et al., “Tailored loss discrimination in indefinite metamaterial-clad hollow-core fibers”, Opt. Express 24, 15702-15709 (2016)