<title>Imaging of surface plasmons with a near-field microscope</title>

Abstract

Imaging of surface plasmon polaritons (SPPs) with a photon scanning tunneling microscope (PSTM) combined with shear force feedback is experimentally investigated. A contrast correction factor, that accounts for spatial frequency filtration performed by an uncoated fiber tip of the PSTM, is introduced and evaluated from the measurements of a standing wave interference pattern formed by two counter- propagating evanescent waves, that are generated by total internal reflection of light beams inside a glass prism. Influence of propagating field components stemming from inelastic SPP scattering on the resultant intensity distribution and, consequently, on the near-field optical images obtained with the PSTM is discussed. Optical images taken at different tip-surface distances are used to evaluate the contribution from propagating field components in near-field optical images taken with shear force feedback. The approach developed is applied to experimental studies of elastic scattering of SPPs excited at the wavelength of 633 nm along smooth and rough surfaces of gold and silver films.