Implications of high resolution to near-field optical microscopy

This paper presents problems inherent to high-resolution near-field optical microscopy. It is shown on an easily understandable level, that high lateral confinement of optical fields (a prerequisite for high-resolution microscopy) leads to a fast decay of the fields. Consequently, the optical probe has to be brought very close to the sample surface, increasing the sensitivity to artifacts. Highly confined optical fields are strongly sensitive to variations in the probe–sample separation. The resulting optical images are, therefore, dominated by topographical variations and do not represent the optical properties of the sample surface.