Core of PC fiber is filled with silica aerogel

Silica aerogel is an extremely porous glass structure with pores on the order of 40 nm in size and air-filling fractions ranging from 86% to 98%.

Nov 1st, 2010

Silica aerogel is an extremely porous glass structure with pores on the order of 40 nm in size and air-filling fractions ranging from 86% to 98%. The material has low refractive index and high optical nonlinearity but is very fragile. Now, researchers at the University of Bath (Bath, England) and the University of Sydney (Sydney, Australia) have managed to fill the core of a hollow photonic-crystal (PC) fiber with silica aerogel, creating a "container" for the material that simultaneously mechanically protects the aerogel and allows high light intensities to be guided in it.

To create the structure, one end of a length of PC fiber was heated to collapse all holes but the 6 μm core. A sol (the precursor to aerogel) was then sucked into one end of the fiber by applying a vacuum at the other end. A 30 cm long core-filled length of fiber was then cut away. After the sol turned to wet gel, the fiber was aged and supercritically "dried" in methanol. Optical attenuation of the finished fiber was about 0.2 dB/cm between 1300 and 1650 nm wavelengths, apart from a 0.6 dB/cm spectral spike at 1400 nm. At longer wavelengths, light was guided by total internal reflection; at shorter wavelengths, a photonic bandgap guided the light. Contact Tim Birks att.a.birks@bath.ac.uk.

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