Subwavelength confinement of light in hyperbolic metamaterials with dielectric nanoparticle coupling

Directed refraction and strong dispersion, which are characteristic properties of hyperbolic metamaterials, make such materials suitable for performing spatial-spectral transformation. This transformation involves encoding of spatial information with resolution beyond the diffraction limit in the scattering spectrum, which may be collected with standard optics in the far-field. This gives rise to potential applications in compressive super-resolution microscopy in which compressive sensing algorithms are used for reconstruction of super-resolved images from a broadband measurement of an objects spectrum illuminated through the hyperbolic metamaterial. For such imaging to be successful, light, which carries subwavelength information, needs to be coupled to high-k modes of a hyperbolic metamaterial. This is required to observe wavelength-dependent directional propagation, which is necessary for the spatial-spectral transformation. Although it is possible to exploit diffraction on nanoholes in a Cr mask to provide additional momentum, this approach suffers from low transmittance which is especially detrimental for compressive imaging applications. In this paper we analyze dielectric spherical nanoparticle arrays as an alternative broadband coupling method with increased efficiency. Light transmittance and concentration are enhanced through photonic nanojets, localized enhanced _elds with low beam divergence. The finite-element method study of the structure is performed to find wavelength-dependent coupling efficiency as a function of nanoparticle size, material as well as array period and configuration. The analysis with effective hyperbolic dispersion relation is further refined to include a metal-dielectric multilayer.