Veselago predicted that a rectangular solid with a negative index of refraction material would make an image of an object right in front of it, with the image created right behind.  Pendry, many decades later, predicted that such a lens would be able to focus the near-field light into an image and avoid the diffraction limit. To catch the near field light, which decays away rapidly with distance from the object, the "superlens" would have to be pressed right up against the object. 

Experimenters worked to make a negative index of fraction lens that would image the shortest wavelength light possible, to make the image as sharp as possible.  Several groups succeeded in building a lens that worked at 1400 nm, about twice the wavelength of red light.

The discovery that a thin film of metal can have a negative index of refraction spurred physicists to fashion superlenses out of these films.  In 2005, groups led by Richard Blaikie in New Zealand and also Xiang Zhang at the University of California, Berkeley succeeded in building a silver superlens that made an image with ultraviolet light (whose wavelength is shorter than that of visible light) and beat the diffraction limit.  Those groups patterned gratings onto a mask, pressed the lens up against the mask, and created their images on photoresist, which undergoes a chemical change upon exposure to ultraviolet light.  The image can be "seen" with an atomic force microscope.

On the left is the object, two nanowires separated by 150 nanometers (nm). In the center is the image made by superlens, which clearly resolves the two wires, even though their separation was much less than the wavelength of the light used to make the image.  On the right, without the superlens, the two wires cannot be resolved. (image credit: Zhang Lab, UC Berkeley)

Here the superlens is imaging wires arranged into letters.  The two arrows on the "N" indicate that the spacing there is 200 nm. (image credit: Zhang Lab, UC Berkeley)

Take a look at Zhang’s images.  His objects were narrow lines--some were part of a grating, and others were fashioned into letters. The width of the letter strokes was 40 nm.  Without the superlens, each stroke in the image had a width of about 320 nm, and with silver-film superlens in place, the width was under 90 nm--about a quarter of the wavelength of the 365 nm light used to make the image.

As far as actual applications are concerned, this revolutionary technology is limited, because the object, the lens, and the image are all right up against each other. But within the field of lithography, which is used to fabricate computer components, the superlens may make it possible to pack more components closer together on a silicon chip.

Negative index of refraction offers the prospect of other other exciting technologies as well. Pendry suggested that if an object were enclosed in a metamaterial, as shown in the diagram, light would be swept around the object, just as if it weren't there--a cloaking device. As physicists like to say, "Whatever is not forbidden is required."

On the left is the object, two nanowires separated by 150 nanometers (nm). In the center is the image made by superlens, which clearly resolves the two wires, even though their separation was much less than the wavelength of the light used to make the image.  On the right, without the superlens, the two wires cannot be resolved. (image credit: Zhang Lab, UC Berkeley)