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Investigation and Analysis of the Effect of Graphene on the Extraordinary Transmission of Light using Circuit Model

Motavassel, Ahmad | 2018

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 50650 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Khavasi, Amin
  7. Abstract:
  8. Subwavelength metallic slit structures allow extraordinary transmission of light (EOT) at certein frequencies.In recent years, the effect of graphene layer on EOT has been investigated, which is used in the design of terahertz modulators. The electrostatic tuning ability of graphene electrical conductivity controls the resonance frequency and the amount of incident radiation absorption. Because of the single atomic thickness of graphene, the wide range control of incident light can not be achieved alone. However, by placing this layer with various 1-D and 2-D patterns on periodic metallic layers with EOT ability, high light modulations can be obtained. In particular, the structure of the periodic metal slits with a graphene ribbon array inside it, has been investigated in various papers by performing simulation and testing the constructed samples.Although there are equivalent circuit models for graphene ribbons or metallic slits separately, but no comprehensive circuit model has been proposed for multi-layered structures consisting of graphene ribbons and periodic metal slits. The circuit model provides faster & better optimization of the structure.Also, by using circuit model, parameteric design can be perfomed in order to study various effects of graphene on EOT.In this research, it is planned to extract a circuit model for multi-layered structure. This structure consists of 1-D periodic metal slit layer & array of gaphene ribbons. For this purpose, electromagnetic waves are expressed by rayleigh expansion. Graphene surface current is expressed by eigenfunction expansion. By constructing boundary conditions at each layers’ boundery, reflection coefficient is found & a circuit model is obtained for different configurations of the structure. Using the circuit model, the frequency depandance of the amount of incident light transmission and it’s dependency on the applied voltage to the graphene, are examined for this structure. By using the circuit model, a multilayer perfect absorber consisting of graphene ribbons, periodic metal slits, and dielectric material, in the terahertz frequency range is designed. With the aid of the resonance coupling of the metal slits and graphene, its bandwidth increases as high as possibe. Also, using circuit model, a terahertz modulator with voltage contorl ability is designed. In all stages, the correctness of the circuit model is tested with the results of software simulation
  9. Keywords:
  10. Graphene ; Circuit Model ; Modulators ; Graphene Ribbon Arrays ; Extraordinary Transmission (EOT)Light ; Periodic Metal Slits ; Perfect Absorber

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