Simultaneous enhancement of radial resolution and side lobe suppression of tubular hyperlens via introducing a nano-gap layer

Conventional metal-dielectric stacked hyperlenses based on hyperbolic metamaterials can reconstruct subwavelength information to the far field without loss, which is an effective method to break the Abbe diffraction limit. However, the radial resolution of most of current hyperlens is not high enough, which maybe hinders their applications in 3D precision imaging. Meanwhile, the presence of strong side lobes in the hyperlens far-field imaging is another issue, which not only weakens the main lobe, but also results in the overlapping of image points of multiple objects and the consequent difficulty in distinguishment. Here we propose a simple and effective method of achieving an incredible radial super-resolution imaging capability while having an outstanding side lobes suppression ratio (SLSR). Our structure for tubular hyperlens consists of alternating 92 pairs of Ag/Yi₂O₃ layers whose inner radius is 400 nm and the thickness of both Ag and Yi₂O₃ is 10nm. Then, we simply introduce the nano-gap layer into hyperlens by replacing Ag and Yi2O3 layers, and guarantee that the nano-gap layer is surrounded by Yi₂O₃ layers and the overall thickness of the hyperlens is unchanged. Corresponding finite element simulation results reveal that the radial resolution reaches the highest accuracy of 3 nm and SLSR achieves more than 3 dB at 365 nm TM-polarized source, which improves the imaging clarity extremely. The hyperlens we designed is of great significance for ultra-precision 3D optical imaging and real-time biomedical imaging. In addition, the application prospect on high performance sensing can be expected due to the super-resolution characteristics.