Hollow-core photonic crystal fibres have excited interest as potential ultra-low loss telecommunications fibres because light propagates mainly in air instead of solid glass. We propose that the ultimate limit to the attenuation of such fibres is determined by surface roughness due to frozenin capillary waves. This is confirmed by measurements of the surface roughness in a HC-PCF, the angular distribution of the power scattered out of the core, and the wavelength dependence of the minimum loss of fibres drawn to different scales.

The light radiated from the guided mode of a hollow core photonic crystal fiber into free space is measured as a function of angle and wavelength. This enables the direct experimental visualization of the photonic band gap and the identification of localized modes of the core region.

Articles you may be interested inSpontaneous quasi-periodic current self-oscillations in a weakly coupled GaAs/(Al,Ga)As superlattice at room temperature Appl.We report the observation of self-sustained photocurrent oscillations in a weakly coupled spatially direct intrinsic GaAs/Al 0.3 Ga 0.7 As superlattice. The oscillations are attributed to the dynamics of unstable electric field domains related to the ⌫Ϫ⌫ e1-e2 tunneling resonance. The observed oscillation period is much longer than the carrier recombination time and the interwell tunneling time. The nonlinear behavior shows a complex dependence on the optical power and the external bias.

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