Imaging with hyperbolic metamaterials: the role of resonant high- <i>k</i> modes and the impact of dielectric loss

The ability of hyperbolic metamaterials to achieve sub-diffraction imaging via high- k wave propagation is intrinsically limited by a narrow operational bandwidth near Fabry-Perot resonances. We elucidate the physical origin of the image artifacts by first modeling the metamaterial slab as a cavity resonator and then refining this picture with a full-wave transfer matrix method (TMM). The cavity resonator model provides an idealized framework for subwavelength imaging by describing the role of discrete transverse modes in the absence of material absorption. In contrast, the TMM approach provides a more realistic description by accounting for the complex anisotropic permittivity and its associated dielectric losses. Our analysis reveals that significant image distortion arises from the resonant amplification of high- k modes. We propose that this resonant behavior can be mitigated by carefully tailoring the dielectric loss within the slab, effectively flattening the transmission of all modes, and restoring broadband imaging capability. Our method offers a significant improvement over existing post-processing techniques, particularly at lower frequencies where distortions are most severe. Finally, we validate our analytical model with full-vectorial numerical simulations, showing excellent agreement and confirming the viability of our loss-engineering strategy for designing robust, broadband sub-diffraction imaging devices.