Experimental Astronomy

, Volume 24, Issue 1–3, pp 1–7 | Cite as

Air-clad fibres for astronomical instrumentation: focal-ratio degradation

Article

Abstract

Focal-ratio degradation (FRD) of light launched into high-numerical aperture (NA) single-annulus all-silica undoped air-clad fibres at an NA of 0.54 is reported. The measured annular light distribution remained Gaussian after 30 m of propagation, but the angular FWHM of the output annulus doubled from 4° after 1 m propagation to 8.5° after 30 m, which is significantly larger than that reported of standard doped-silica fibres (NA < 0.22). No significant diffractive effects were observed. The design of air-clad fibres for broad-band, high-NA astrophotonics applications is discussed.

Keywords

Focal-ratio degradation High-numerical aperture Air-clad fibres 

Notes

Acknowledgements

We acknowledge funding of this work through Australian Research Council (ARC) Discovery Project grants as well as technical expertise in fibre fabrication and funding from K. Lyytikäinen-Digweed, S. Huntington, J. Digweed and S.D. Jackson.

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Copyright information

© Springer Science+Business Media B.V. 2008

Authors and Affiliations

  1. 1.Interdisciplinary Photonics Laboratories, School of ChemistryUniversity of SydneySydneyAustralia

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