First flat lens puts focus on light polarisation

The one micron thick ‘flat’ lens is claimed to offer performance comparable to high-end compound lens systems. The findings of the team, led by Nanfang Yu, associate professor of applied physics at Columbia University, New York, are detailed in Light: Science & Applications.

Conventional lenses route light through different paths so that the whole light wave arrives at the focal point simultaneously. Such lenses are manufactured to do so by adding an increasing amount of delay to the light as it goes from the edge to the centre of the lens.

With the goal of inventing a thinner, lighter, and cheaper lens, Yu's team took a different approach. Using their expertise in optical metasurfaces - engineered two-dimensional structures - to control light propagation in free space, the researchers built flat lenses made of pixels, or so-called ‘meta-atoms’

Each meta-atom is said to have a size that is a fraction of the wavelength of light and delays the light passing through it by a different amount. By patterning a very thin flat layer of nanostructures on a very thin substrate, the researchers achieved the same function as a much thicker and heavier conventional lens system.