Vector theory of diffraction by a single-mode fiber: application to mode-field diameter measurements.
We derive a far-field diffraction integral by (vector) electromagnetic theory; the result differs from the (scalar) Rayleigh-Sommerfeld or Kirchhoff result in that it depends on polarization. For unpolarized light, we derive a factor (1 + cos(2) theta)((1/2))/ radical2 that replaces the usual obliquity factor. Omitting this factor can cause an error of the same order as the measurement uncertainty in determining the mode-field diameter of a single-mode fiber from far-field data.
Young
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Wittmann
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