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In 'near field scanning optical microscopy' ('NSOM', also 'SNOM') a very small light source very close to the sample is scanned. Light passes through a sub-wavelength diameter aperture and illuminates a sample that is placed within its near field, at a distance much less than the wavelength of the light. The resolution achieved is far better than that which is attainable in conventional optical microscopes.
Near field scanning optical microscopy (NSOM) was developed in the mid 1980's as a means to break the diffraction limit on spatial resolution attainable with optical measurement. Traditional NSOM utilizes a tapered, metal-coated optical fiber with a small aperture as either an excitation source or collection device. The spatial resolution attainable with this technique is roughly defined by the size of the aperture itself. Unfortunately, rough metallic coatings on glass fibers, coupled with the finite skin depth of metals at optical frequencies, place a limit on the spatial resolution attainable with fiber probes. Typical spatial resolution for the fiber approach to NSOM is ~50-100 nm, though careful probe and sample preparation have yielded ~30 nm resolution.

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External links

See also

★ Nano-optics

External links

★ Extensive and detailed introduction to NSOM