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Evanescent‐wave scattering in near‐field optical microscopy
Author(s) -
Wannemacher R.,
Quinten M.,
Pack A.
Publication year - 1999
Publication title -
journal of microscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.569
H-Index - 111
eISSN - 1365-2818
pISSN - 0022-2720
DOI - 10.1046/j.1365-2818.1999.00519.x
Subject(s) - scattering , mie scattering , multipole expansion , optics , polarization (electrochemistry) , dielectric , molecular physics , excitation , light scattering , near field scanning optical microscope , total internal reflection , extinction (optical mineralogy) , materials science , physics , optical microscope , chemistry , optoelectronics , scanning electron microscope , quantum mechanics
Extended Mie theory is used to investigate the scattering and extinction of evanescent waves by small spherical particles and aggregates of such particles. Metallic, dielectric and metal‐coated dielectric particles are taken into consideration. In contrast to plane‐wave excitation, p ‐ and s ‐polarized spectra differ in the case of evanescent waves due to the inherent asymmetry of both polarizations. Furthermore, contributions from higher multipoles are strongly enhanced, compared with plane‐wave excitation, and the enhancement factors are polarization dependent. The corresponding changes in the scattering and extinction spectra are most pronounced in cases where higher multipoles exhibit resonances in the spectral range considered. This applies, for example, to morphological resonances of dielectric particles with size parameters > 1. The effect of the surface, where the evanescent wave is generated by total internal reflection, on the scattering and extinction spectra is investigated via numerical field calculations employing the multiple multipole method. In an application to apertureless near‐field optical microscopy, the variation of the scattered power is calculated when a silicon particle is scanned across a silver particle in the evanescent field.