Superlens gives microscopes a new look

A new type of lens made of metamaterials may break the limit for optical microscopes, and show images things as small as viruses and the internal structures of a cell.

Modern optical microscopes are limited at how far down the scale range they can go by physical properties on light. Details finer than half of the wavelength of light – which is about 200 nanometers for the lower violet part of the visible spectrum – are lost as the light scatters, interferes, and detracts off the object. Smaller things like viruses and molecules can only be imaged by other instruments such as electron microscopes or atomic force microscopes.

However, this limit can be circumvented by using so-called "evanescents." They are formed as the light crosses between media with differing optical properties, and decay exponentially with distance so they can only be picked very close to the object in the region called “near field."

Superlenses that can collect these evanescent waves and convert them into normal light waves that can be observed by an optical microscope were invented back in 2007 in the US. However, those were greatly limited in terms of light spectrum and application.

Now, a team at the University of Hamburg in Germany have developed a new design that could produce 2D images of 3D nanoscale objects across the entire visible, and some of the infrared, spectrum. Their work is published in the Physical Review Letters journal, as New Scientist magazine reports.

The new superlens is a lattice made of silver, silicon, gallium, indium and arsenic, which rolls itself in layers in a tiny tube. If an object is placed inside the tube, which has a gap of around 2,000 nanometers inside, the lens collects evanescent waves near its surface. As they pass through, it magnifies them to a point where they can be seen by a light microscope positioned perpendicular to the lens.

The team headed by Stefan Mendach is now working on making the lens layers thinner so that more of them can be rolled together. This will allow greater magnification in the superlens.