Meteoritic dust from the atmospheric disintegration of a large meteoroid.

Much of the mass of most meteoroids entering the Earth's atmosphere is consumed in the process of ablation. Larger meteoroids (> 10 cm), which in some cases reach the ground as meteorites, typically have survival fractions near 1-25 per cent of their initial mass. The fate of the remaining ablated material is unclear, but theory suggests that much of it should recondense through coagulation as nanometre-sized particles.

Small-core single-mode microstructured polymer optical fiber with large external diameter.

A preform sleeving technique is demonstrated that allows the fabrication of single-mode polymer microstructured fiber with the smallest core and hole dimensions yet reported to our knowledge. For a fixed triangular hole pattern a range of fibers is produced by adjustment to the operating conditions of the draw tower. Numerical modeling is carried out for one of the fibers produced with a 570-microm external diameter, a core diameter of 2.

Identifying hollow waveguide guidance in air-cored microstructured optical fibres.

An analysis of leaky modes in real microstructured optical fibres fabricated specifically for photonic band gap guidance in an air core has been used to identify alternative guiding mechanisms. The supported leaky modes exhibit properties closely matching a simple hollow waveguide, uninfluenced by the surrounding microstructure. The analysis gives a quantitative determination of the wavelength dependent loss of these modes and illustrates a mechanism not photonic band gap in origin by which colouration can be observed in such fibres.

Bragg gratings in air-silica structured fibers.

We report on grating writing in air-silica structured optical fibers with pure silica cores by use of two-photon absorption at 193 nm. A decrease in propagation loss with irradiation was observed. The characteristic growth curves were obtained.

Retaining and characterising nano-structure within tapered air-silica structured optical fibers.

Air-silica fiber 125m in diameter has been tapered down to ~15m. At this diameter, it is commonly assumed that the nanostructured fiber holes have collapsed. Using an Atomic Force Microscope, we show this assumption to be in error, and demonstrate for the first time that structures several hundred nanometers in diameter are present, and that hole array structures are maintained.