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Fabrication and Characterization of Carbon Nanotube Network Film-based Optical Devices Using Femtosecond Laser Machining
- Author(s)
- 민태열
- Advisor
- 염동일
- Department
- 일반대학원 에너지시스템학과
- Publisher
- The Graduate School, Ajou University
- Publication Year
- 2020-02
- Language
- eng
- Alternative Abstract
- 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.
- Fulltext
- Appears in Collections:
- Graduate School of Ajou University > Department of Energy Systems > 3. Theses(Master)
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