Measurement of the transmitted intensity from a coherent monomode lightsource through a series of subwavelength slit arrays in Ag films, with varyingarray pitch and number of slits, demonstrate enhancement (suppression) by asmuch as a factor of 6 (9) when normalized to that of an isolated slit.Pronounced minima in the transmitted intensity were observed at array pitchescorresponding to lambda_SPP, 2lambda_SPP, and 3lambda_SPP where lambda_SPP isthe wavelength of the surface plasmon polariton (SPP). Increasing the number ofslits to more than four does not increase appreciably the per-slit transmissionintensity. These results are consistent with a model for interference betweenSPPs and the incident wave that fits well the measured transmitted intensityprofile.
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