A simplified analytic model is employed to demonstrate how surface plasmons propagating between the slits in Young's interference experiment can modulate the spatial coherence of the light field radiated by the two slits. The model is verified by comparison with results from rigorous numerical simulations. Our simulations reveal that the coherence can indeed be enhanced or suppressed, depending on the distance between the slits. Extending our analysis to a three-slit geometry, the effect on the degree of modulation when another slit is placed between the two slits is investigated. It is found that, compared to the two-slit case, the center slit serves not only as a barrier that can reduce the modulation, but can also act to enhance the amount of modulation. These results are promising for the development of novel "coherence converting" devices with suitable metallic arrays of subwavelength apertures.
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Gan et al. (2008) studied this question.