Abstract

An Airy pattern results from the Fraunhofer diffraction of a plane wave passing through a circular aperture [1, 2], like the light of a star passing through a telescope mirror with perfect seeing. At most 80% of an Airy pattern can couple to the fundamental mode of a conventional single-mode fibre. We report a fibre with a graded refractive index distribution, Fig.1(a), in which it is possible to couple a calculated ~95% of the Airy pattern into one of its guided modes. We designed the index profile so that the mode matched the central disc and the first 3 bright rings of the Airy pattern. In this way we could achieve both performance (i.e. to guide a very close approximation to the Airy pattern), and feasibility (i.e. ability to fabricate the fibre).

© 2015 IEEE