The Berkeley team improved their silver-film superlens by adding 35-nanometre-wide corrugations to its surface. These diffract light waves from an object's near-field, turning them into normal light waves. The superlens was able to distinguish two wires positioned just 70 nm apart – a resolution nearly three times better than that of conventional optics.
Conventional lenses can only see details roughly down to the size of half the wavelength of light. This limit is due to interference and diffraction that occurs as light bounces off an object.
A superlens gets around this limit by collecting light waves that only occur very close to an illuminated object. These "evanescent waves" contain information about at finer resolution but are hard to use because these waves decay rapidly. The nanometre-scale region in which they exist is known as the "near-field".
Being able to project the super-resolution image beyond the near-field could make the superlens much easier to use, Zheludev says. "But the lens still has to be positioned close to the object to be in its near-field," he points out.
A superlens that could focus on objects from beyond the near-field would be truly revolutionary, he adds. "There are suggestions that it's possible, but we don't know for sure.