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Near-field Optical Probing Of Fluorescent Microspheres Using A Photon Scanning Tunneling Microscope
Published 1996 · Materials Science
We report on the direct near-field probing of fluorescent polystyrene microspheres using a Photon Scanning Tunneling Microscope. An optical fiber tip frustrates the evanescent part of the light existing in the near-field of the sample. We combine classical and fluorescence near-field probing, in the photon tunneling configuration and demonstrate a novel effect which, to our knowledge, has not been reported yet. An improvement of the discrimination of the microspheres is observed in near-field when fluorescence light is emitted owing to the presence of an evanescent part of the fluorescence light in the vicinity of the sample. This part which is normally compelled to remain confined to the near-field of the sample is converted into propagating light by the probe and this tunneling fluorescence light brings additional information about the sample. This effect is highly sensitive to the incident (i.e., excitation) wavelength and it is found that when the observed confinement is maximum, a slight change in the incident wavelength entails noticeable changes in the near-field images.