Plasmon-enhanced optics and magneto-optics via the near field of a nanowire

摘要

A general theory is developed for surface-plasmon-enhanced near-field optics and magneto-optics via a linear nanoprobe. Considered as a model is a nanowire located near a sample with an embedded magnetic nanolayer, both nanoobjects being parallel to the surface of the sample. The nanowire is thought of as a thin noble-metal cylinder which possesses long-lived surface plasmons, and so can do the surface of noble-metal sample. With the electrodynamic Green function technique, a resonant polarization response of the complex "probe+image" is treated self-consistently within a multiple-scattering approximation. The magnetization-linear scattering events are classified in terms of TM (p-polarized) and TE (s-polarized) waves, the polarization planes of incident and scattered waves coinciding. The problem of resonant near-field magneto-optics with a linear probe is solved analytically for a nanolayer magnetized along its normal (polar magneto-optical Kerr effect). As well, in varying the in-surface distance between the near-field probe and a laterally nanosized magnetic domain, the scanning near-field microscopy in scattering mode is treated. Polarization, angle and spectroscopy characteristics of the magneto-optical resonant scatterings due to a nanowire are found and shown to differ principally from those due to a quasi-point probe. Resonant enhancement of scattering efficiency due to coupled surface plasmons of a nanowire and a sample is estimated.