A Bright Future for Subwavelength Light Sources
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The amount of data you can burn on a compact disk or DVD hinges,
fundamentally, on the spot size of each data bit. Recording devices
that rely on a focusing lens are restricted by the physical
diffraction limit, but very small spot sizes can alternatively be
made by passing the light through a tiny hole. The roadblock
is that holes that are much smaller than a wavelength in size
typically do not allow much light to go through. Surprisingly, when
the area surrounding the hole has surface corrugations, the power
throughput of even very small holes can be enhanced considerably, to
the point that it is useful for data recording. Although she
was once a staunch supporter of the idea that a phenomenon called
surface-plasmon resonance accounted for this effect, the author has
recently come to champion an entirely different explanation: the
diffraction and interference of evanescent waves.