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Analysis of Time-Varying Epsilon-Near-Zero and Zero-Index Metamaterials

Heidarzadeh, Parham | 2022

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 55898 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Memarian, Mohammad; Mehrany, Khashayar
  7. Abstract:
  8. Epsilon-near-zero media have attracted considerable attention in the last decade due to their exceptional behavior in wave propagation. The purpose of this research project is to analyze time-periodic ENZ structures. To this end, layered structures consisting of plasmonic metal and dielectric layers are used to achieve the epsilon-near-zero effect in a specific frequency range, and by time-variations of the dielectric layers, an effective time-varying (TV) ENZ is achieved. A method based on transfer matrix method is developed to analyze such structures while they are undergoing time-variations, and primarily under normal incident waves. Various structures based on such TV layered structures are studied both in the reflective and transmission configurations. Exceptional wave propagation phenomena are observed such as many-harmonic generation, odd harmonic elimination, etc, which may find different applications as in frequency combs. These effects are shown to be achieved primarily due to the extreme modulation index (~1000) achievable using a time-periodic ENZ structure. This extreme modulation index is the result of a low modulation strength, divided by an almost zero average (static) index. This is while in conventional TV media with a non-zero static index, it is impossible to actually realize such high modulation index values, as very high modulation strengths would be required. Every single structure that has been studied during this research project is followed up by an effective model of itself. The validity of approximations that has been made during this research is verified by comparing the result of these two sets of structures
  9. Keywords:
  10. Metamaterial ; Layered Structure ; Frequency Harmonic Generation ; Epsilon-Near-Zero ; Time-Varying Structures ; Layered Structures Consist of Metal and Dielectric Layers

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