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Analysis and Characterization of Near Field Behavior of Plasmonic Nanostructures

Heydarian, Hesam | 2020

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 53088 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Rashidian, Bizhan
  7. Abstract:
  8. Despite ongoing progress in the field of nanophotonics, characterizing and identifying optical interactions in the deep subwavelength dimensions have remained challenging. The inability of conventional optical microscopy in nanoscale imaging, due to diffraction limit, was the main stimulus for research on new characterizing methods with the capability of non-destructive high-resolution imaging in which the sample preparation is not required. To achieve this goal, scanning probe microscopes are introduced to extract valuable high spatial harmonics from near field measurements on the sample. In this thesis, by focusing on the probe-sample interaction, the near field behavior of the plasmonic nanostructures are studied. First, we review the fundamental concepts and operating principles of the scanning probe microscopes. Subsequently, by studying the structural details of the near field scanning optical microscope (SNOM), its major limitations, including the speed, accuracy and contrast of imaging, as well as unwanted probe-sample coupling are identified. In order to relieve these limitations, we propose, and design a new class of SNOM probes, known as plasmonic multi-color aperture probes. We demonstrate that these probes can generate more than one hot spot with well-known spatial distribution to simultaneously image multiple points on the sample. This not only enables one to calibrate out many sorts of errors in conventional SNOM, but also results in the increase in the speed and contrast of imaging. In the next step, by examining the near field interaction between the probe and the sample, we show that strong tip- sample coupling can lead to unwanted red shift in the spectral characteristic of the structure image. This limitation can be compensated by a blue shift in spectral response, achieved by utilizing the tunability of the chemical potential of graphene in multicolor probes
  9. Keywords:
  10. Scanning Probe Microscopy ; Near Field Optic ; PLasmonic Structure ; Surface Plasmon ; Plasmonic Nanoparticles ; Optical Characterization

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