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Design and Study of Lenses with Resolution Beyond the Diffraction Limit

Zivari, Amir Parsa | 2019

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 52543 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Rejaei, Behzad; Khavasi, Amin
  7. Abstract:
  8. In this article some systems wich have a resolution beyond the diffraction limit and much more than the conventional lenses (like convex lenses, optical microscopes that have a resolution in order of wavelength) have been reviewed. These structures can be used in many different areas like Electron-Beam lithography (Photoleptography and Nano lithography), printing integrated optical circuits and chips, accurate cell imagings (entering and exiting of proteins in cells) and etc. This kind of imaging is called ”subwavelength imaging”. Generally some remarkable properties of these structures are propagation of all the spatial frequencies or amplifying the evanescent waves. One of the most known structures for this application is a left handed material which enjoys negative refraction. In fact in these kind of media, group velocity and phase velocity are anti directional which results to negative refraction. Implementing of these structures usually is done artificially with metamaterials. In this thesis, some of structures that have been used until now in order to break through the diffraction limit, like surface waves, metamaterials with negative permittivity and permeability and plasmonic wave guides, will be studied and introduced and also two recent new structures, which are Graphene-Semiconductor structure and Dielectric-Ag Metal, for implementing left handed plasmonic surface waves will be introduced and studied. By using the former mentioned new structure (Graphene on GaAs) a deeply subwavelength resolution in order of 84 may be achieved. Moreover, there is another common approach for subwavelength imaging; Hyperbolic Media. In these media the isofrequency contours are Hyperbolic like (instead of Spherical) and thus, they have no evanescent mode. These media are introduced and studied in this thesis and it has been shown that if the enjoy a nearly flat isofrequency contour, they are a perfect candidate for subwavelength imaging. At the end, high temperature superconductors will be studied as a hyperbolic material with a huge anisotropy which makes them a great candidate for subwavelength imaging. It is also shown that one can achieve a deeply subwavelength resolution(in the order of 1000 using them.Additionally, their far-field imaging and magnification features will be studied in advan
  9. Keywords:
  10. Imaging ; Lens ; Diffraction Limit ; Negative Refraction Phenomenon ; Graphene ; Superconductivity ; High Temperature Superconductor ; Hyperbolic Space

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