Applications of near field optical microscopy: Fluorescence in situ hybridisation, Langmuir-Blodgett films and integrated optical waveguides

Scanning Near-field Optical Microscopy (SNOM), based on metal coated adiabatically tapered fibres, combined with shear force feedback and operated in illumination mode, has proven to be the most powerful SNOM arrangement, because of its true localisation of the optical interaction, its true optical contrast (fluorescence, polarisation, etc.) and its sensitivity down to the single molecular level. We present the first application of SNOM to (i) Fluorescence In Situ Hybridisation (FISH) of human metaphase chromosomes, where the localised fluorescence allows to identify specific DNA sequences in addition to the topographic force image, and (ii) Langmuir-Blodgett mono-layers, where the orientation of the polymer backbone and the degree of polymerisation is visualised in the near-field polarised fluorescence simultaneously with the topography in the force signal.

Photon Scanning Tunnelling Microscopy (PSTM), based on frustration of total internal reflection with uncoated dielectric probes and operated in transmission mode, is experimentally easier than aperture SNOM, but less straightforward in its interpretation as generally near field and far field scattering are observed mixed with topographic effects. We have applied combined PSTM/AFM to (i) Langmuir-Blodgett mono-layers, and (ii) integrated optical ridge waveguides. Both systems have virtually no surface structure. In the waveguides purely the electric field distribution is probed by coupling to the evanescent wave. Direct observation by PSTM of TM and TE modal field distributions, mode beating and application to a Y-junction wavelength (de)multiplexer is presented.