Super-resolution imaging through a planar silver layer.

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.