Development of Variable - Temperature Near-Field Scanning Optical Microscope

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A near-field scanning optical microscope (NSOM) will be designed and constructed to study samples in the temperature range 10 K to 400 K. Light in the wavelength region 1500 to 400 nanometer range will be channeled down a fiber-optic wave guide to a tapered end with an aperture of size 20 to 200 nanometers positioned just above the sample surface. The NSOM is capable of resolution more than an order of magnitude smaller than the diffraction limit and is the only optical technique capable of probing structures with features on a scale much less than 1 micrometer. The NSOM will be employed for the study of spatial variation of the current flow in high-temperature Josephson junctions. Defects near the junction interfaces cause inhomogeneous current flow, but the characteristics and distribution of the defects are largely unknown. A second project will study the spatial dependence of the optical emmission from conducting polymer light-emitting diodes. The NSOM tip will act as a localized collector of light emitted from the sample. A near-field scanning optical microscope will be developed to study spatial imhomogeneities on a scale much less than the diffraction limit of ordinary light. The microscope will operate in the temperature regime 10 K to 400 K and will be used to study the spatial variation of the electrical current in high temperature superconductor Josephson junctions and, secondly, the spatial variation of light emitted from conducting polymer light-emitting diodes.