Three–dimensional finite–difference time–domain study of enhanced second–harmonic generation at the end of a apertureless scanning near–field optical microscope metal tip

http://www.opticsinfobase.org/abstract.cfm?URI=josab-22-5-1045We use a finite-difference time-domain method to model the experiments of second-harmonic generation at the apex of a metallic tip used in a scanning near-field optical microscope. We calculate the linear diffracted field and the second-harmonic field. In the near field we compare the confinement of the two fields around the apex. In the far field we determine the spectral responses versus the sample tip coupling