Effect of nanohole spacing on the self-imaging phenomenon created by the three-dimensional propagation of light through periodic nanohole arrays

We present a detailed study of the inter-nanohole distance that governs the self-imaging phenomenon created by the three-dimensional propagation of light through periodic nanohole arrays on plasmonic substrates. We used scanning near-field optical microscopy (SNOM) to map the light intensity distributions at various heights above 10 × 10 nanohole arrays of varying pitch sizes on silver films. Our results suggest the interhole spacing has to be greater than the wavelength of the incident light to create the self-imaging phenomenon. We also present finite-difference time-domain (FDTD) calculations which show qualitative corroboration of our experimental results. Both our experimental and FDTD results show that the self-imaging phenomenon is more pronounced for structures with larger pitch sizes. We believe this self-imaging phenomenon is related to the Talbot imaging effect that has also been modified by a plasmonic component and can potentially be used to provide the basis for a new class of optical microscopes.