Near-, mesoscopic and far-field regimes of a subwavelength Young's double-slit

The coupling distance between two narrow resonating slits made in a thick metal screen strongly modulates the optical spectral features of their scattering resonances. We show that these non-trivial modulations result from dipolar-type interactions between the slits. The radiation damping, frequency shift and local light enhancement of these modes vary with the coupling distance, and we derive analytical expressions for these physical quantities. We also explain how transmission and antenna-like radiation pattern can be tuned with specific incidence angles.