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Design of Terahertz Low Loss Waveguides Based on Periodic Dielectric Structures

Tehranian, Ali | 2018

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 51590 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Ahmadi Boroujeni, Mehdi
  7. Abstract:
  8. In this project, we report on two waveguide structures suitable for implementing terahertz compact devices. First structure is composed of a periodic array of metallic blocks attached to a metal plate at the bottom. By integrating the metallic teeth in a silicon ridge and then evacuating the space between metal blocks, we enhanced the field confinement. At last by putting a metal plate over the structure at a proper distance in order to enhance the normal component of the electric field to the upper face of the metal blocks as main component of power transmission, in addition to even more field confinement, we isolated the structure from outside world. We assessed waveguidng properties of the proposed structure in 2D version of the structure of infinite width by mode matching method and in 3D version of finite width by mode analysis with the help of commercial fullwave simulators. It can be seen that by proper design, we can realize subwavelength bent waveguides with very low bending loss. Bending loss as low as 0.2 dB for a 〖90〗^°-bend of radius of nearly one quarter of free space wavelength at the end of the frequency band (300 GHz) was achieved in a bandwidth of one octave. More over, the proposed waveguide has much larger operational bandwidth rather than conventional waveguides of this kind. We also improved mechanical stability of the structure. Due to high propagation loss in metal-based structures, another structure is proposed. In this structure, metallic blocks are replaced with high index dielectric materials. There is no dielectric ridge covering dielectric blocks. This structure is also investigated in 2D problem of infinite width with multimode network theory and in 3D problem of finite width by mode analysis using commercial fullwave simulators. We show that propagation losses in this structure is deacreased because of the replacement of metal blocks with dielectric blocks. Average loss factor of 3 Np/m was calculated for the proposed structure which is comparable with the loss factors of dielectric waveguides. Aslo, we show that the performance of this structure is better than conventional metallic structures in terms of field confinment, operational bandwidth, bending loss, physical stability and system isolation
  9. Keywords:
  10. Waveguide Devices ; Periodic Structure ; Spoof Plasmonic Waves ; Modal Analysis ; Waveguide Bend ; Plasmonic Waveguides

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