3-DIMENSIONAL MODELING OF AMPLITUDE-OBJECT IMAGING IN SCANNING NEAR-FIELD OPTICAL MICROSCOPY

The imaging properties of the transmission-illumination mode of a scan ning near-field optical microscope are investigated. Three-dimensional calculations of the power transmitted into classically allowed and fo rbidden regions for a nonsymmetrically positioned amplitude object are implemented by use of the finite-difference time-domain solution of M axwell's equations. The evolution of the images with the distance from the object as well as the effect of the polarization of the illuminat ion is shown. The computations show that for applications involving th e imaging of an amplitude object, the use of the allowed Light is pref erred. Collection of light from both the allowed and the forbidden zon es leads to degraded contrast and resolution. (C) 1998 Optical Society of America.