Impedance effect on imaging of far-field hyperlens with geometrically increasing layer thicknesses

The hyperlens with flat dispersion curve and geometrically growing layer thicknesses are designed to project an object to the far field beyond the diffraction limit. Three hyperlens structures (two are our hyperlens structures and the other is a structure with varying local permittivity for layer pairs in radial direction) are considered in infrared and it is found that our hyperlens structures have better performance in reducing losses within the structure and finally improve the quality of the imaging. Fabry-Perot resonance effect periodically influences the sharpness of the point source focusing as the total thickness begins to increase from a certain value, especially for the impedance matched structures. As the thickness of the outermost layer is much less than the effective wavelength of the hyperlens, the most important issue influencing the resolution ability of the system is the magnification factor. We systematically study the performance of our hyperlens as the innermost radius r 1 and e 1 change. We find that for our hyperlens structures the impedance is not the most important issue for magnification imaging. Different parameters should be purposefully chosen for our hyperlens according to the practical requests (e.g., resolution or intensity) and our research results can provide a good guidance in the structure designing.