Spectroscopic Imaging in the Near Field with an Apertureless Solid Immersion Lens Microscope

摘要

To achieve high lateral resolution in microscopy, we exploit the localized electromagnetic field of a Solid Immersion Lens (SIL). The lens is mounted on a cantilever of a Scanning Probe Microscope (SPM) to allow a dynamic scan with constant tip-sample force. This unit can be integrated into a micro fluorescence (Zeiss UMSP) or Raman spectrometer (Renishaw) to allow spectroscopy and spectrally resolved imaging in the near field. Three methods can be applied with a lateral resolution of less than 30 nm: 1) Reflectance-SNOM: the sample is imaged by illuminating the surface through the SIL and detecting the reflected near-field. 2) Photon-tunneling-SNOM: the contrast is generated by the ability of the photons to tunnel through the energy barrier into the substrate. 3) Fluorescence- SNOM: the chromophore is excited and the fluorescence light is collected by the SIL. The collection efficiency for the fluorescence is increased by a factor of 10 due to the high refractive index of the SIL compared to conventional methods.