All-solid bandgap guiding in tellurite-filled silica photonic crystal fibers.

We report all-solid bandgap-guiding fibers formed by pumping molten tellurite glass into silica-air photonic crystal fiber at high pressure. The spectral positions of the guidance bands agree well with multipole simulations and bandgap calculations. The micrometer-diameter tellurite strands are found to contain microheterogeneities (most probably originating from devitrification), which increase the fiber attenuation, although no evidence of crystallization is seen in the bulk tellurite glass. The technique offers a potential route to employing difficult-to-handle glasses, or glasses unsuitable for fiber drawing, in fiber-based amplifiers, modulators, filters, and nonlinear devices.