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Analysis and Design of Optical Devices by Colloidal Nano-Structures

Nekuee, Amir Hossein | 2016

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 48312 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Akbari, Mahmood
  7. Abstract:
  8. The colloidal crystals are formed of spherical particles and can be fabricated using simple and low-cost chemical methods. Optical properties of colloidal crystals should be recognized properly in order to design optical devices based on these nano-structures. Reflection and transmission coefficients of these multilayer structures are very important for understanding their properties. Semi-analytical methods like Fourier Modal method (FMM) can be very useful to obtain their reflection and transmission properties of these multilayer structures. In this thesis, we try to implement Matched Coordinate (MC) and Adaptive Spatial Resolution (ASR) techniques in the FMM. These techniques increase convergence rate and the accuracy of numerical results in the analysis of two-dimensional colloidal crystals especially hybrid colloidal crystals.In the following, guided modes of two-dimensional colloidal structures are extracted using phase changes of transmission and reflection coefficients and then band structures of these structures and their inverse replica are obtained. The existence of band gap for odd or even modes in these structures is very important. These gaps confine guided modes in the horizontal plane while the control of light in the vertical direction is done by the principle of total internal reflection. Therefore by these structures we can made waveguides that control light in three-dimensions.Hybrid colloidal crystals that are made of colloidal particles and a material with plasmonic properties can be important in optical devices. Graphene is one of these materials that due to its unique properties, has been highly interested. In this thesis, by modelling the graphene as a surface conductivity, FMM formulation is modified in such a way that Fourier factorization rules have been applied correctly. This new formulation greatly reduce the computational cost and running time. This formulation can be used in the analysis of hybrid colloidal structures that are designed by graphene such as broadband absorbers.Hybrid colloidal crystals can be fabricated by combining the colloidal crystals and the metasurfaces.In this chapter new boundary conditions using the susceptibility distribution of the metasurafce are introduced such that without solving any eigenvalue equation the characteristics of the metasurface such as reflection, transmission and absorption can be calculated easily. Correct Fourier factorization rules are also applied in the proposed boundary conditions that increase the convergence rate of this method in comparison with the previous works. This formalism can be used in the analysis of hybrid colloidal structures that are made by metasurfaces
  9. Keywords:
  10. Semi-Analytical Solution ; Reflection Coefficient ; Colloidal Crystals ; Fourier Factorization ; Phase Variations ; Diffracted Orders

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