Soft-glass photonic-crystal fiber transmits singlemode, broadband light

Researchers at the Max Planck Institute for the Science of Light (Erlangen, Germany) have developed the first soft-glass, hollow-core photonic-crystal fiber to offer singlemode broadband light guidance at wavelengths from 750–1050 nm at a transmission loss of only 0.74 dB/m. Such large-core fibers are useful for particle guidance and fluid- and gas-filled device applications.

Soft or compound glasses such as heavy-metal oxides, fluorides, and chalcogenides have much lower melting points than silica glass and have the potential to transmit infrared light for applications in mid-IR spectroscopy, lidar, and materials processing. However, these low-temperature processing points also mean that to date, light-guiding soft-glass fibers have only been demonstrated with solid cores and limited-wavelength transmission capabilities. But by developing a custom-designed spiral-shaped heating element to minimize temperature fluctuations and glass devitrification during the draw process, the research team was able to produce—through fast-feeding and slow-drawing rates—a hollow-core, photonic-crystal fiber from Schott SF6 lead-silicate glass (with a refractive index of 1.82 at 500 nm) consisting of an approximate 30-µm-diameter hollow core surrounded by a six-layer, kagomé-type lattice cladding. Finite-element calculations determined that the unique singlemode confinement of the fiber is due to the presence of triangular interstitial gaps in the fiber geometry created during the draw process, as well as the high index of the glass material.

Contact Xin Jiang at [email protected].