APPARENT SUPERRESOLUTION IN NEAR-FIELD OPTICAL IMAGING OF PERIODIC GRATINGS

A superresolution phenomenon in images of diffraction gratings obtaine d with a near-field optical microscope probe positioned at distances o f the order of 1 mu m from the surface was recently reported [Appl. Op t. 33, 876 (1994)]. This experiment was interpreted in terms of evanes cent waves observed in the far field. We show that the effect observed in that experiment is a very well known far-field optical phenomenon called the Talbot effect. The existence of self-imaging Talbot planes for gratings with periods of the order of a few micrometers appears pr omising for many practical applications. (C) 1998 Optical Society of A merica.