Development of novel photonic switching devices based on low-dimensional carbon nanostructures for compact pulsed lasers
Development of novel photonic switching devices based on low-dimensional carbon nanostructures for compact pulsed lasers
- 주제(키워드) low-dimensional carbon nanostructure , saturable absorber , pulsed laser , compact laser
- 발행기관 아주대학교
- 지도교수 이상민
- 발행년도 2015
- 학위수여년월 2015. 2
- 학위명 박사
- 학과 및 전공 일반대학원 에너지시스템학과
- 실제URI http://www.dcollection.net/handler/ajou/000000019663
- 본문언어 영어
- 저작권 아주대학교 논문은 저작권에 의해 보호받습니다.
초록/요약
Low-dimensional carbon nanostructures such as carbon nanotubes (CNTs) and graphene have been among the most interesting materials studied in recent decades. The inherently fast response time, broadband linear absorption, and third-order nonlinearity of singlewalled CNTs (SWCNTs) and graphene enable the application of these materials as ultrafast broadband optical-switching devices, such as saturable absorbers (SAs). Owing to the superior properties of carbon-nanostructure-based SAs, excellent mode-locking performance has been demonstrated compared with the results achieved using conventional semiconductor saturable absorber mirrors (SESAMs). Compared with SESAMs, carbon nanostructures are more flexibly applied as SAs. To date, SWCNT and graphene are the most frequently used SAs for ultrafast pulsed lasers. However, despite the substantial results regarding carbon-nanostructure-based SAs, research on the broadband application and engineering of SA parameters, e.g., the linear and nonlinear absorption properties, has not yet been conducted. In this thesis, the linear and nonlinear properties of SWCNT and graphene SAs are controlled by various approaches. The delicate handling of carbon-nanostructure materials leads to the uniform and low scattering losses of devices. By controlling the concentrations and thicknesses of the SWCNT-SAs on transparent or reflective substrates, the linear absorption of the devices can be modulated between less than 1% and over 30%. High-quality, largearea, single-layer graphene is also fabricated, and flake-based graphene is suggested to compensate for the limited gap of 2.3% intrinsic linear absorption per layer of the welldefined single-layer graphene. The nonlinear optical characterization of the parameter controlled carbon-nanostructure-based SAs is performed in the broadband spectral region. The fast recovery time of the devices is revealed for both the SWCNT and graphene SAs, indicating that nonlinear optical properties can be engineered by modulating the linear absorption of the devices using high-resolution nonlinear transmission measurements. According to the parameter engineering technique, a novel type of SA for the compact-fiber and bulk-laser system is suggested, including an all-in-one multifunctional SA mirror. The varying thickness of the carbon-nanostructure SA on asymmetry structured platform, polarization-dependent, evanescent field-coupled optical properties of the devices are controllable. Material-injected fibers are also developed, for a robust and relatively long nonlinear evanescent wave interaction in the fiber-laser system. Furthermore, sub-cm waveguides are proposed for the device integration. These multifunctional, novel carbonnanostructure- based SAs have been demonstrated for fiber and bulk solid-state laser modelocking and ultra-compact waveguide laser Q-switched operations. Evanescent-waveinteraction- type SWCNT and graphene-injected holey fibers exhibit a robust and relatively high power operation compared with previous carbon-nanostructure-based SAs. The application of an all-in-one SA on a single dielectric mirror is successfully demonstrated, whereby the 30-cm-long laser cavity generates 150-fs pulses. The Q-switching operation of the channel waveguide laser is also achieved using a modulation-depth-controlled SWCNTSA mirror. Total length of 1-cm-long laser cavity with an SWCNT-coated output coupler exhibits a stable Q-switched pulse generation; this is basic research for SWCNT and graphene-based SA-mode-locked ultra-compact waveguide lasers.
more목차
Abstract ..................................................................................................................... i
List of figures .......................................................................................................... vi
List of tables ............................................................................................................ xi
1. Introduction .......................................................................................................... 1
References ......................................................................................................................... 4
2. Low-dimensional carbon nanostructures for ultrafast optical switching
devices ................................................................................................................... 6
2.1. Low-dimensional carbon nanostructures .................................................................... 6
2.1.1. Graphene ............................................................................................................. 6
2.1.2. Single-walled carbon nanotubes (SWCNT) ........................................................ 9
2.2. Low dimensional carbon nanostructures for nonlinear optical devices .................... 12
2.3. SWCNT and graphene saturable absorber for ultrafast pulse generation: issues and
motivation ........................................................................................................................ 15
References ....................................................................................................................... 18
3. Fabrication and characterization of low-dimensional carbon nanostructurebased
saturable absorbers ................................................................................ 20
3.1. Fabrication process of carbon structure based-SAs .................................................. 22
3.1.1. Fabrication of SWCNT-SAs .............................................................................. 22
3.1.2. Fabrication of graphene-based SAs ................................................................... 25
3.2. Characteristics of SWCNT-SAs ............................................................................. 27
3.2.1. Visualizing SWCNT and graphene ................................................................... 28
3.2.2. Raman spectroscopy of SWCNT and graphene-based SAs .............................. 30
3.2.3. Linear optical properties of SWCNT and graphene-based SAs ........................ 35
3.2.4. Nonlinear optical characterization of SWCNT and graphene-based SAs ......... 40
References ....................................................................................................................... 52
4. Superior characteristics of novel carbon-nanostructure-based SAs for
compact pulsed laser systems ........................................................................... 61
4.1. Polarization-dependent evanescent wave interaction scheme of carbonnanostructure-
based SA ................................................................................................... 63
4.1.1. Carbon nanostructure-deposited side-polished fiber ......................................... 64
4.1.2. The waveguide type carbon-nanostructure-based SA ....................................... 69
4.2. Polarization-independent, evanescent wave interaction scheme of carbonnanostructure-
based SAs; carbon-nanostructure-filled hollow optical fibers .................. 72
4.3. Multifunctional carbon-nanostructure-based SAM for compact bulk solid-state
lasers ................................................................................................................................ 78
References ....................................................................................................................... 82
5. Application of novel carbon-nanostructure-based SAs for compact pulsed
laser systems ....................................................................................................... 88
5.1 Mode-locking of Er-doped fiber laser using carbon nanostructure-filled HOF ........ 89
5.1.1. Er-doped fiber laser mode locked with SWCNT-filled HOF SA ...................... 89
5.1.2. Er-doped fiber laser mode locked with graphene-filled HOF SA ..................... 91
5.2. Compact, diode-pumped bulk solid-state laser mode-locked using carbonnanostructure-
based-SAM ............................................................................................... 94
5.3. Q-switched operation of diode-pumped femtosecond-laser inscribed channel
waveguide laser using SWCNT-SA ................................................................................ 99
References ..................................................................................................................... 107
6. Conclusions and prospects .............................................................................. 113
List of publications ............................................................................................... 116
