Deep-Subwavelength Focusing and Reflectionless Negative Refraction in Visible-Light Hyperbolic Metasurface

Hyperbolic metasurfaces (HMSs) are artificially-engineered interfaces, exhibiting high anisotropy manifested as hyperbolic dispersion. Their ability to support extremely large momenta with negative diffraction and refraction places them as promising platforms for on-chip super-resolution and enhanced light-matter interaction. While the hyperbolic nature of these structures is experimentally demonstrated, only a limited number of studies have concentrated on their super-resolution capabilities, which are never obtained at visible-frequency for fully harnessing their immense resolution potential. Here, a near-field investigation of visible-frequency HMSs is presented, exploiting their super-resolution capabilities to their maximum potential. The impulse response of waves propagating across HMSs is measured and demonstrates deep sub-wavelength anomalous focusing and on-chip reflectionless negative refraction at the interface of parabolic and hyperbolic media, independent of incident angle. The approach lays the foundation for sub-wavelength imaging in 2D space for the advancement of imaging and wave compression devices, leveraging the capabilities of HMSs.