PHASE IMAGES OF GROOVES IN A PERFECTLY CONDUCTING SURFACE

Scattering of an arbitrary two-dimensional electromagnetic field by an isolated rectangular groove in a perfectly conducting substrate is modeled using a rigorous electromagnetic diffraction formalism. By calculating the phase of that part of the scattered field, which propagates in directions that fall within the numerical aperture of a microscope objective, we examine the resolution limits of a Linnik-type interference microscope with focused coherent illumination, It is shown that accurate groove width and depth determination by phase measurement should be possible, even when the groove width is somewhat smaller than the optical wavelength, if use is made of reference data obtained by rigorous computations. However, our results do not support some recent experimental results that suggest the possibility of achieving superresolution by interference microscopy.