Evanescent waves, rulers of the nanoworld
Nanoimagery by near-field optical microscopy

As we saw earlier, Rayleigh's criterion establishes a physical barrier that renders details smaller than half the illumination wavelength unobservable. In the course of its propagation, light loses the information it contains concerning these small details, just as if the medium in which light propagates were a filter for sub-wavelength details, and therefore a low-pass filter for spatial frequencies (figure 2 ). When we illuminate an object...