Fabrication and Characterization of Carbon Nanotube Network Film-based Optical Devices Using Femtosecond Laser Machining
Fabrication and Characterization of Carbon Nanotube Network Film-based Optical Devices Using Femtosecond Laser Machining
- 주제(키워드) Carbon Nanotube Network Film , Femtosecond Laser Machining
- 발행기관 아주대학교
- 지도교수 염동일
- 발행년도 2020
- 학위수여년월 2020. 2
- 학위명 석사
- 학과 및 전공 일반대학원 에너지시스템학과
- 실제URI http://www.dcollection.net/handler/ajou/000000029936
- 본문언어 영어
- 저작권 아주대학교 논문은 저작권에 의해 보호받습니다.
초록/요약
Carbon nanotube (CNT) network films exhibit optically homogeneous properties despite the random network structure of single-walled carbon nanotubes (SWCNT) used as thin films. In addition, the substantial gate-turnability of the Fermi energy of the CNT network film in a near-infrared range can result in a large optical modulation because of its unique band structure. Furthermore, CNT network films can be easily fabricated over a large area and its thickness is also easily controllable by using a spin-coating method. In this paper, we develop and characterize several optical devices based on CNT-network film patterned by a direct laser machining (DLM) method. The DLM method can be an efficient technique to fabricate a desired pattern on a CNT thin film without a photomask. The amplified femtosecond laser source is used for the DLM setup, and the focused femtosecond pulses can ablate various materials without changing the wavelength of the pulse by virtue of nonlinear process. we first built an automated DLM system and successfully fabricate a diffraction grating and a Fresnel zone plate for the target wavelength of 1550nm on the CNT network thin film having a thickness of 60nm. The diffraction grating and Fresnel zone plate reasonably works compared to the previous devices based on low dimensional materials. Especially, the Fresnel zone plate can focus the light effectively at the designed focal length with the focal spot having a lateral full-width half-maximum of 0.98. Moreover, we fabricate a gate-tunable device based on the CNT network thin film pattered by the diffraction grating using the DLM method. We observed strong optical modulation of almost 76% in the first order power of the diffracted beam through the ion-gel-based gating for the applied gate voltage within 2V. This ambiguously large modulation may arise from the interference nature of the first order diffraction from the grooves of the diffraction grating.
more목차
Chapter 1. Introduction 1
Chapter 2. Carbon nanotube(CNT) network film 4
2.1 General Properties of CNT 4
2.2 Carbon Nanotube(CNT) network as thin film 7
2.3 Determination of Complex Refractive Index of CNT network film 10
Chapter 3. Direct laser machining (DLM) 14
3.1 Direct ablation using ultrafast laser 14
3.2 Set-up and remarks 18
3.3 Basic fabrications on CNT network film for optimization 20
Chapter 4. Pattern fabrication on CNT network film using DLM 27
4.1 Device pattern designs 27
4.2 Pattern Fabrication 28
4.3 Verification on operation of devices 31
Chapter 5. Gate-tunable optical devices with patterned CNT network films 34
5.1 Diffraction grating 34
5.2 Fresnel zone plate 38
Chapter 6. Discussion 39
6.1 Summary 39
6.2 Future works 40
References 41
국문요약 44
