Realization of optical superlens imaging below the diffraction limit

Recently, the concept of superlensing has received considerable attention for its unique ability to produce images below the diffraction limit. The theoretical study has predicted a 'superlens' made of materials with negative permittivity and/or permeability, is capable of resolving features much smaller than the working wavelength and a near-perfect image can be obtained through the restoration of lost evanescent waves (Pendry 2000 Phys. Rev. Lett. 85 3966-9). We have already demonstrated that a 60 nm half-pitch object can indeed be resolved with λ₀/6 resolution with the implementation of a silver superlens with λ₀= 365 nm illumination wavelength, which is well below the diffraction limit (Fang et al 2005 Science 308 534-7). In order to further support the imaging ability of our silver superlens, a two-dimensional arbitrary object with 40 nm line width was also imaged (Fang et al 2005 Science 308 534-7). In this paper, we present experimental and theoretical investigations of optical superlensing through a thin silver slab. Experimental design and procedures as well as theoretical studies are presented in detail. In addition, a new superlens imaging result is presented which shows the image of a 50 nm half-pitch object at λ₀/7 resolution.