Air-clad fibres for astronomical instrumentation: focal-ratio degradation
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.
- Publication:
-
Experimental Astronomy
- Pub Date:
- May 2009
- DOI:
- 10.1007/s10686-008-9132-7
- Bibcode:
- 2009ExA....24....1A
- Keywords:
-
- Focal-ratio degradation;
- High-numerical aperture;
- Air-clad fibres