Modification of the focused field in a parabolic index medium by slow axial tapering.
We investigate the effect of slow axial tapering on the 3-D structure of the light distribution at the foci of a parabolic index medium. Our approach is based on an adiabatic local mode representation of the field and leads to simple expressions for the field distribution and intensity widths, for any taper shape provided it satisfies a slowness criterion. This slowness criterion unifies the results given here with previously published work.
Bertilone
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