Squeezing Light Through Nanoholes

Light can easily penetrate through holes in macroscopic openings such as windows, however openings that are comparable in size to the wavelength of light are difficult to penetrate. Scientists at Northwestern have demonstrated that light can squeeze through holes that are significantly smaller than the wavelength of light by using thin gold films that support plasmon excitation and a diffraction effect known as the Rayleigh anomaly. The sensitivity of this effect to adsorbed molecules makes it possible to use it for a new class of biomolecular sensing.

The schematic on the left shows a metal film with holes that light can either penetrate or reflect from, depending on the hole size compared to the wavelength. On the right is an electromagnetic field calculation which shows efficient transmission of light from bottom to top through a hole.