In principle a “perfect lens” could be created that opens up a brave new world of scientific investigation, particularly in nanotechnology and the biosciences. The key requirement of these instruments is to devise a cunning way of getting around the diffraction limit, which restricts the resolution of images produced with optical light. This film takes you to Imperial College London to investigate one promising route to a perfect lens that uses artificial structures known as metamaterials.
Light is, of course, a wonderful thing as it can be guided and focused using simple lenses and fibres, capturing images of objects that are either too small or too far away to be seen with the naked eye. Moreover, many atomic and molecular transitions occur at optical wavelengths, which is why light – from the infrared to the ultraviolet – lies at the heart of a vast range of spectroscopic techniques. But there is one major drawback to light as a probe of atoms and molecules: light of a certain wavelength cannot be used to discern an object smaller than about half that wavelength. Even for ultraviolet light, this “diffraction limit” is about 50 nm, or roughly the size of a large protein molecule.
One promising route around the diffraction limit is to create a lens using so-called metamaterials, which contain structures that are smaller than the wavelength of light. “By arranging those structures in certain ways you can amplify light waves and get them to diffract the wrong way and you can see images you wouldn’t normally be able to see, on a much smaller scale,” explains science communicator Chris Clarke. The idea of creating a perfect lens using metamaterials was first proposed in 2000 by Sir John Pendry of Imperial College London and the basic principles have already been demonstrated experimentally.
Today at Imperial College, bioscientists are starting to speculate about how they might use such a sophisticated imaging tool in their research. “What these high-resolution microscopies are beginning to reveal is that there are a lot of exceedingly small structures down to the level of ten of nanometres or less. And these structures are critical to the way cells talk to each other,” explains Iain Dunlop, a biomaterials scientist. “When your immune system decides if it’s going to attack something, there are spatial structures at that size which are helping to mediate that decision. So the ability to image those is vital to understanding that.”
This film is one of a three-part series exploring some of the most promising technologies that are emerging from physics research. You can read about other physics spin-offs by downloading the special 25th anniversary issue of Physics World as a free PDF.