Flat lens uses quantum effects to mimic optical focusing

Economist : Traditional lenses focus light by taking advantage of refraction. By varying the width of the lens, one can change the path of the photons and, hence, the amount of refraction. A new lens, however, created by Federico Capasso and his colleagues of Harvard University, uses the quantum effects of nanostructures to focus light through a flat surface by absorbing the photons, holding on to them for a short time, and then releasing them. Capasso’s team used electron-beam lithography to create a pattern of concentric rings of antennae from a 60-nm-thick layer of gold on a silicon wafer. By varying the shape and separation of the antennae, the researchers were able to vary the length of time each ring would trap the photons before re-emitting them, which resulted in a focused beam of light. Because the distance between the antennae must be shorter than the wavelength of the light, the lens currently only works with monochromatic light. Nevertheless, the lens could be very useful in single-color laser optics, where variances inherent in glass lenses can decrease lasers’ effectiveness.