Published online by Cambridge University Press: 22 March 2004
A realistic near-field calculation on metallic holesamples in illumination transmission conditions predicts certainlight confinements around the holes. The purpose of this paper isto explain theoretically how an A-SNOM (Apertureless ScanningNear-field Optical Microscope) is able to detect the lightconfinement around the holes, and how it is possible, by defininga criterion of separation between two holes in near-field, toanalyse the resolution as a function of the experimentalparameters. The modulation of the probe height in A-SNOM is usedfor both distance control and separation of the near-field fromthe background scattered light. A realistic model of lock-indetection is used to calculate the images of test samples.Constant height mode images are presented at different amplitudesof probe modulation and average heights of the tip. We alsodiscuss the detection at different demodulation harmonics.