Enhancement and manipulation of terahertz nonlinearity
- 주제(키워드) terahertz wave , terahertz nonlinearity , nonlinear organic crystal , ultra-subwavelength structure , electron tunneling , mode conversion
- 발행기관 아주대학교
- 지도교수 Fabian Rotermund, Dong-Il Yeom
- 발행년도 2017
- 학위수여년월 2017. 2
- 학위명 박사
- 학과 및 전공 일반대학원 에너지시스템학과
- 실제URI http://www.dcollection.net/handler/ajou/000000024979
- 본문언어 영어
- 저작권 아주대학교 논문은 저작권에 의해 보호받습니다.
초록/요약
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.
more목차
Chapter 1. Introduction 1
Chapter 2. Generation of an efficient broadband THz pulse using a nonlinear organic crystal 5
2.1 Terahertz electromagnetic wave 6
2.2 Photoconductive antenna 7
2.3 Optical rectification in nonlinear optical crystals 10
2.4 Electro-optic sampling for THz pulse detection 15
2.5 Optical rectification via Organic crystal for broadband THz spectrum 19
2.5.1 Optical properties of electro-optic OHQ-T crystal 21
2.5.2 Efficient ultra-broadband terahertz wave generation beyond 10 THz 28
2.6 Efficient THz wave generation by direct pumping at Ti:sapphire wavelength 37
2.6.1 Characteristics of efficient few-cycle terahertz radiation 39
2.6.2 High-power organic THz wave generator 46
2.6.3 Efficient THz wave generation with new electro-optic salt crystals 60
2.7 Conclusions 69
Chapter 3. Enhancement of the THz field nonlinearity in ultra-subwavelength structures 70
3.1 Theoretical Background and experimental concept 71
3.2 Experiment setup of Nonlinear THz spectroscopy 72
3.3 Giant field enhancement in angstrom-gap of graphene 74
3.3.1 Angstrom-Sized Quantum Barriers 74
3.3.2 Nonlinear optical response in transmission 78
3.3.3 Tunneling conductivity inside the gap 84
3.4 THz wave funneling enabled electron tunneling in Al2O3 nano-gaps 90
3.4.1 Transmission measurement in metallic gap structures 94
3.4.2 Comparison with dc tunneling measurements 98
3.5 Conclusion 104
Chapter 4. Manipulation of the THz field nonlinearity 105
4.1 Mode - Vortex generation of intense THz field for novel THz nonlinear photonic 106
4.1.1 The basic principles of Vortex beam 107
4.1.2 High-power broadband THz vortex generation 110
4.1.3 Nonlinear transmission of graphene by utilizing THz vortex 119
4.1.4 Mode conversion for super resolution THz imaging 125
4.2 Spectrum - THz spectral filling by Complementary Tandem configuration 135
4.2.1 Design of Tandem THz Generators 137
4.2.2 Single Organic THz Generators 141
4.2.3 Tandem Cell Configurations 144
4.2.4 Frequency Dependence in Organic Tandem THz Generators 148
4.3 Conclusion 153
Chapter 5. Conclusion 154
Bibliography 157
Publications list 177
