Negative and Positive Impact of Roughness and Loss on Subwavelength Imaging for Superlens Structures

摘要

We study on the negative and positive effect of surface roughness and loss coefficient on subwavelength imaging of the superlens structure. It has been found that even though surface roughness enables more transmission of high spatial frequency components, the random interferential noise between neighborhood images becomes more severe with increasing distortion. We show that additional loss is able to restrain the interferential noise caused by random roughness while preserving the imaging integrity. The results with practical parameters prove that the mean contrast and uniformity are improved by adding adequate loss on rough surface. Moreover, other two situations are further studied:(a) a single superlens with roughness on different interfaces and (b) a multilayered alternated metal-dielectric superlens with roughness on each surface. We found that the roughness on the imaging surface (metal-photoresist interface) plays a major role in determining the superlens imaging. The multilayer superlens is able to enhance the subwavelength imaging with fractionalized thinner films. But with the further fractionizing layers, the multilayer becomes more vulnerable to the roughness due to the multiple mixing and distorting. We still prove that additional loss is able to improve the performance in both situations.