Optics in the diffraction limit: principles, results, and problems

Abstract

ses through a diaphragm in a metal screen and reaches the sample, which is in the `near field' (NF) of the source. If the distance z to the sample surface and the radius a of the aperture are much smaller than the wavelength l of the light, a, z # l, the size of the light spot on the sample is close to the size of the aperture. When the probe is moved along the sample, the resolution may not be restricted by diffraction (such resolution is known as `super-resolution'). Although such an idea was proposed as long ago as 1928 by Syngh [1], it was far ahead of its time and was practically left unnoticed. Its first confirmation was obtained in 1972 in microwave experiments carried out by Ash and Nichols [2]. At the beginning of the 1980s Pohl, Denk, and Lanz of the IBM Zurich Research Laboratory `penetrated' the diffraction limit and demonstrated a resolution of l#20 on a