Ultra-high-Resolution, Label-Free Hyperlens Imaging in the Mid-IR

The hyperbolic phonon polaritons supported in hexagonal boron nitride (hBN) exhibiting long scattering lifetimes are advantageous for applications like super-resolution imaging via hyperlensing. Yet, challenges exist in hyperlens imaging to distinguish individual and closely spaced objects and in correlating the complicated hyperlens fields with the structure of an unknown object underneath the hyperbolic material. Here, we make significant strides to overcome each of these three challenges. For the first two, we demonstrate that monoisotopic h11BN (> 99% 11B) provides the ability to experimentally resolve structures as small as 40-nm and those with sub-25-nm spacings, inferring at least 154- and 270- times smaller than free-space wavelength, showing improvements in spatial resolution. We also present an image reconstruction algorithm that provides a structurally accurate, visual representation of the embedded objects using only the hyperbolic dielectric function and thickness as input parameters. Further, we offer additional insights into the frequency dependence for realizing optimal hyperlens performance. Thus, our results significantly advance label-free, high-resolution, spectrally selective hyperlens imaging and image reconstruction methodologies.