It has been proposed that a planar silver layer could be used to project a super-resolution image in the near field when illuminated near its plasma frequency [J. B. Pendry, Phys. Rev. Lett. 86, 3966 (2000)]. This has been investigated experimentally using a modified form of conformal-mask photolithography, where dielectric spacers and silver layers are coated onto a tungsten-on-glass mask. We report here on the experimental confirmation that super-resolution imaging can be achieved using a 50-nm thick planar silver layer as a near-field lens at wavelengths around 365 nm. Gratings with periods down to 145 nm have been resolved, which agrees well with our finite-difference time domain (FDTD) simulations.

Optical imaging through a thin planar silver layer has been achieved by utilizing near-field lithography techniques. A 120 nm thick silver lens that was placed 60 nm below a patterned mask, imaged the mask’s features onto a photosensitive material located 60 nm below the silver. The entire structure was exposed from above with a mercury lamp. Features sizes as small as 350 nm (at a 700 nm period) were imaged onto the photosensitive material, demonstrating the lensing ability of the planar silver slab.

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