Experimental observation of Ag nanowire scattering illuminated by evanescent wave

Ag nanowires are not only a good surface plasmon waveguide, but also a fabulous converter to transfer a propagating wave into a bonded surface wave and vice versa. In this paper, we investigate the scattering properties of single Ag nanowire illuminated by evanescent wave. Since the Ag nanowire can be regarded as a dipole radiator chain in p-polarized evanescent illumination, the wide-field microscopic image of the scattering field can be well explained by diffraction integration in the deep Fresnel region. Moreover, the scattering of a v-shaped Ag nanowire is also investigated in evanescent wave illumination. Because of the orientation-dependent scattering of the Ag nanowire, the scattering field beneath the nanowire can either intercross or not, depending on the propagating direction of the incident evanescent wave, which is observed by a scanning confocal microscope in the z-scanning mode. The interference between the intercrossing scattering waves result in a non-diffracted beam and the direction of the generated non-diffracted beam can be controlled as well. (paper)