Analysis and simulation of a fiber bundle method for creating a partially spatially coherent beam.

ABSTRACT

A fiber bundle arrangement containing a distribution of fiber lengths has been proposed in the literature to produce a partially spatially coherent beam. Light input to the bundle with limited temporal coherence is translated into limited spatial coherence. Expressions are developed for the bundle pupil autocorrelation function and far-field irradiance pattern. A numerical simulation approach is implemented and results are compared with a speckle-free result. The fiber bundle approach tends to create an irradiance pattern whose average shape matches the pattern produced by a single fiber. A "smoothed" far-field pattern is obtained if the fiber length difference is much greater than the source temporal coherence length.