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Enhancement and manipulation of terahertz nonlinearity
- Author(s)
- 강봉주
- Advisor
- Fabian Rotermund, Dong-Il Yeom
- Department
- 일반대학원 에너지시스템학과
- Publisher
- The Graduate School, Ajou University
- Publication Year
- 2017-02
- Language
- eng
- Keyword
- terahertz wave; terahertz nonlinearity; nonlinear organic crystal; ultra-subwavelength structure; electron tunneling; mode conversion
- Alternative Abstract
- In this thesis, (i) efficient broadband terahertz (THz) wave generation using a nonlinear organic crystal, (ii) giant enhancement of the electric field in an ultra-subwavelength structure, and (iii) the manipulation of the THz field nonlinearity with an additional degree of freedom are investigated in various ways based on nonlinear interactions with novel materials and structures. We begin by introducing an efficient broadband THz wave generation beyond 10 THz with a strong 650-kV/cm electric field generated by a collinear optical rectification method utilizing the considerable nonlinear properties of an organic electro-optic crystal realized by suitable molecular structures. For the first time, using angstrom- and nano- sized structures, electromagnetic field funneling to λ/10,000,000 gaps and a substantial field enhancement (~7000) are observed, resulting in light-driven electron tunneling. With nonlinear THz time-domain spectroscopy, based on the nature of the single-cycle THz pulses, the nonlinear optical properties are then characterized to provide invaluable information on novel light-matter interaction on a quantum scale. Additionally, manipulating the THz electromagnetic wave, we have successfully demonstrated for the first time, a highly intense broadband THz vortex generation utilizing a polymeric Tsurupica spiral phase plate in combination with tilted-pulse-front optical rectification in a prism-cut LiNbO3 crystal. Unique nonlinear absorption and spatial transmission behaviors in graphene are investigated based on the orbital angular momentum of the THz vortex. A time-space synchronized THz mode mapping system is also designed for a super-resolution THz imaging system. A tandem THz-emitting cell as a multilayer organic THz source is also proposed, achieved by the orientational stacking of different organic electro-optic crystals. The organic tandem cell exhibits marked spectral enhancement (>230%) near the phonon deep with a 4.3-times tuning of the spectral bandwidth.
- Fulltext
- Appears in Collections:
- Graduate School of Ajou University > Department of Energy Systems > 4. Theses(Ph.D)
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