Tailored loss discrimination in indefinite metamaterial-clad hollow-core fibers

We analyze the modal attenuation properties of silica hollow-core fibers with a gold-wire based indefinite metamaterial cladding at 10.6 µm. We find that by varying the metamaterial feature sizes and core diameter, the loss discrimination can be tailored such that either the HE₁₁, TE₀₁ or TM₀₁ mode has the lowest loss, which is particularly difficult to achieve for the radially polarized mode in commonly used hollow-core fibers. Furthermore, it is possible to tailor the HE₁₁ and TM₀₁ modes in the metamaterial-clad waveguide so that they possess attenuations lower than in hollow tubes composed of the individual constituent materials. We show that S-parameter retrieval techniques in combination with an anisotropic dispersion equation can be used to predict the loss discrimination properties of such fibers. These results pave the way for the design of metamaterial hollow-core fibers with novel guidance properties, in particular for applications demanding cylindrically polarized modes.