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Nano-optics is the branch of optical
engineering
which deals with optics at deeply subwavelength length scales. Technologies
in the realm of nano-optics
include near-field scanning optical
microscopy (NSOM), photoassisted scanning tunnelling microscopy,
and surface plasmon optics. Traditional
microscopy makes use of diffractive elements to focus light tightly in order
to increase resolution. But because of the diffraction limit
(also known as the Rayleigh Criterion), propagating light may be focused to a
spot with a minimum diameter of roughly half the wavelength
of light. Thus, even with diffraction-limited confocal microscopy, the maximum resolution obtainable is on the order of a couple
of hundred nanometers.
The scientific and industrial communities are becoming more interested in the
characterization of materials and phenomena
on the scale of a few nanometers,
so alternative techniques must be utilized. Scanning Probe Microscopy (SPM)
makes use of a "probe", (usually either a tiny aperture or
super-sharp tip), which either locally excites a sample or transmits local
information from a sample to be collected and analyzed.
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