Phys. Rev. Lett. 109, 097405 (2012)

In contrast to conventional lenses, superlenses allow imaging with, in principle, unlimited resolution. Losses in the structure significantly reduce the image quality of superlenses, however, which has hampered their use for practical applications. To improve performance, Jean-Jacques Greffet and colleagues now suggest a new approach that also looks at the temporal properties of the light beam used for imaging. Superlenses are based on plasmonic surface waves that amplify not only the far-field but also the near-field evanescent waves from the object, which is crucial to achieve unlimited resolution. These plasmonic surface waves are, however, dampened by electric losses. As Greffet and colleagues have discovered, this turns out to be one of the limits to superlens performance. They studied the imaging properties of superlenses where, in contrast to the usual continuous-wave light, optical pulses are used whose duration is shorter than the surface plasmon decay time, so that associated losses are avoided. In numerical computations, such pulses are indeed predicted to lead to sharper images, promising a new approach to superlens imaging.