NSOM microscopy

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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.