Abstract

Photonic crystal fibres (PCFs) with wavelength-scale solid-cores and large air-filling fractions provide dramatic enhancement of optical nonlinearity due to tight optical field confinement between the hollow channels [1]. An example is stimulated Brillouin scattering (SBS), a key optoacoustic nonlinear effect with many important applications [2]. SBS can be greatly enhanced in small-core PCFs compared to standard all-solid fibres, and the holey structure also significantly alters acoustic vibrations in the core, resulting in a family of distinct acoustic modes and a multi-peaked Brillouin gain spectrum [3,4]. Here we report the results of a detailed study of the dependence of the backward SBS spectrum on the core diameter d_core and air-filling fraction a_F. A series of fibres with different core sizes and air-filling fractions were fabricated on a customized drawing tower, using the conventional stack-and-draw technique. The core diameters ranged from 1.4 μm to 5 μm, with air-filling fractions between 0.7 and 0.9. Scanning electron micrographs (SEMs) of four of these fibres are shown in Fig.1(a).

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