Scanning near-field optical microscope having a medium denser than air in the gap between the probe chip and the sample being measured

This scanning near-field optical microscope is of the type where a light beam (19) with a diameter of at maximum lambda /20 is emitted, or received, by a sharply pointed probe tip (13) which is scanned across the surface of a sample (11) to be investigated. The light reflected by, and/or transmitted through, the sample (11) is detected by a detector (16) and/or further processed by a computer (24). The distance between the light-emitting probe tip (13) and the sample (11) under investigation is on the order of lambda /20 as well, so that the surface of the sample (11) is within the near-field of said probe tip (13). This optical microscope is characterized in that the gap between the probe tip (13) and the sample (11) is filled with a liquid (40) of high opacity, including any liquids with a large negative dielectric constant epsilon , so as to attenuate the intensity of the lightwaves emitted or received by the probe tip (13) to such an extent that the penetration depth z0 of the lightwaves inside the liquid, defined as the distance over which their intensity decreases to 1/e, is below 100 nm.