Near-field optical microscopy of fractal structures

摘要

Using a photon scanning tunneling microscopecombined with a shear-force feedback system, we image bothtopographical and near-field optical images (at the wavelengthsof 633 and 594 nm)of silver colloid fractals. Near-field opticalimaging is calibrated with a standing evanescent wave pattern.Near-field optical images exhibit spatially localized (within 150-250 nm) intensity enhancement (by up to 20 times) in the form ofround bright spots, whose positions and brightness are found tobe sensitive to the light wavelength, polarization and angle ofincidence. The observed phenomenon is related to thelocalization of resonant dipolar eigenmodes in random surface nanostructures.