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November 30 (Wed) ~December 2 (Fri), 2011 Hanwha Phoenix Park, PyeongChang Organized by OSK / Photonics Division KICS / Optical Communication Division IEEK / Optical Wave

1 November 30 (Wed) ~December 2 (Fri), 2011 Hanwha Phoenix Park, PyeongChang Organized by OSK / Photonics Division KICS / Optical Communication Division IEEK / Optical Wave and Quantum Electronics Division KIEE / Optical Electronics and E.M. Wave Division IEEE / PS Korea Chapter SPIE / Korea Chapter Program Proceeding Exit

2 Photonics Conference 2011

4 Photonics Conference 2011/W1C-Ⅳ2 Ge 나노입자가첨가된특수광섬유의제조및비선형광특성 Fabrication and nonlinear optical properties of optical fiber incorporated with 정성묵 *, 주성민, 전수원, 김영웅, Weiwei Fan, 한원택 광주과학기술원정보기전공학부 / 광공학응용물리학제전공 The germano-silicate optical fiber incorporated with was developed for nonlinear optical applications by using MCVD and drawing processes. The enhanced non-resonant nonlinear refractive index, n 2, of the fiber measured by the cw-spm method was found to be m 2 /W due to the incorporated. 최근비선형특성이우수한광섬유는 Supercontinuum generation, Optical parametric oscillator (OPO) 및 Optical parametric amplifier (OPA) 등을비롯하여근적외선레이저의 Mode-locking 및 Q-switching, Optical convertor, All-optical switch (AOS) 등에활용가능하여높은관심을모으고있다 [1]. 좁은 Band-gap 및빠른응답특성을갖는비선형광섬유는광섬유코어영역내에희토류이온, 반도체 Quantum dots, 금속나노입자및전이금속이온등을고용하여비선형광특성을향상시키는방향으로연구가진행되고있다 [1, 2]. 본연구에서는광섬유코어영역내에 Ge 나노입자를첨가한특수광섬유를제조하고, 이의비선형성을측정함으로써 Ge 나노입자가함유된특수광섬유의비선형광소자로의활용가능성을평가하고자한다. Fig 1. Schematic of the non-resonant optical nonlinearity measurement set-up using the cw-spm method 그림 1에광섬유의 Non-resonant 비선형광특성을측정할수있는 Continuous-wave self-phase modulation (cw-spm) 방법의개략도를나타내었다. 증폭기를통해증폭된서로다른파장의입력신호들과측정대상인광섬유를통해나온출력파형을비교한후, 이들의 Phase 변화를측정하여다음의식 (1) 과 (2) 를통해비선형굴절률 (n 2 ) 및 nonlinear parameter(ϒ) 를얻을수있다 [1, 2]. n λa ϕ SPM 2 = = 4πL PAVG λa 4πL SPM γ = = = κ a c 2π n 2 1 ϕ κ λ A 2L PAVG 2L 여기서 A 는 area, L 는 length, φ SPM 는 Phase shift, 그리고 κ ac 는 Phase shift와 Input power에따른 Slope coicient를의미한다. Ge 나노입자가함유된특수광섬유를제조하기위해 Modified chemical vapor deposition (MCVD) 공정과 Drawing tower (DT) 를이용하였다. 광섬유코어영역에 Ge 나노입자를고용시키기위하여증류수에 45 μm 직경의 Ge powder (Kojundo, GEE05PB) 를 0.1몰의농도를갖도록첨가하여도핑용액을만들어 MCVD 공정을통해제작된광섬유모재의 Porous layer 부분에침지 a c (1) (2) 9

5 Photonics Conference 2011/W1C-Ⅳ2 토록하였다. 제조된모재를 2000 o C의고온인출공정을통해 125 μm 구경을갖는 Ge 나노입자가함유된특수광섬유를인출하였다. Cut-back 방식을이용하여 Ge 나노입자가함유된특수광섬유의흡수스펙트럼과 Ge 나노입자가함유되지않은광섬유의흡수스펙트럼을비교함으로 Ge 나노입자에의한광특성을평가하였다. 그림 2에서보는바와같이 Ge 나노입자가함유된광섬유흡수스펙트럼의경우 nm 및 nm에서광흡수가일어났으며, 이는광섬유코어에함유된 Ge 나노입자에의한것으로판단된다. 그림 3에 Ge 나노입자가함유된특수광섬유의입력파워에따른 cw-spm 출력파형을나타내었다. cw-spm 출력파형의 I 0 (Zero-order harmonic signal) 과 I 1 (First-order harmonic signal) 을비교하여측정된 Phase shift를식 (1) 과 (2) 를이용하여비선형굴절률 (n 2 ) 과 nonlinear parameter(ϒ) 값을측정한결과각각 4.95x10-20 m 2 /W와 1.62 W -1 km -1 였다. Ge 나노입자가함유된특수광섬유를본연구실에서제조된단일모드광섬유와비교한결과, 측정한비선형굴절률 (n 2 ) 및 nonlinear parameter (ϒ) 는각각 2.1 배및 2 배로증가하였다. Absorption coicient (cm -1 ) nm nm With Without Cut off wavelength Wavelength (nm) OH absorption Fig 3. The cw-spm spectra of the optical fiber incorporated with Ge nano- particles at different input powers Fig 2. Optical absorption spectra of the optical fiber incorporated with and without Ge nano-particles Output power (dbm) I 0 I nm (2w1-w2) nm(w1) nm(w2) Wavelength (nm) nm (-w1+2w2) mw mw mw mw mw mw mw Table 1. Parameters of the optical fiber incorporated with and without [1] Fiber Refractive index difference length core area Slope coicient Nonlinear refractive index nonlinearity Symbol Δ L A κ ac n 2 γ Unit % m μm 2 rad/w m 2 /W W -1 km -1 Optical fiber without x Optical fiber with x 본연구는한국연구재단의중견연구자지원연구사업 (No ), 광주과학기술원재원인 Photonics 2020 및 BK-21의지원에의하여수행되었다. 참고문헌 [1] Y. Kim, S. Ju, S. Jeong, and W.-T. Han PHOTONIC PROPERTIES OF TI DOPED OPTICAL FIBER," Journal of Nonlinear Optical Physics & Materials, 19, pp , [2] H. J. Cho, A. Lin, S. Moon, B. H. Kim, and W.-T. Han, Non-resonant optical nonlinearity of germano-silicate optical fiber incorporated with Si nanocrystals, Journal of the Korean Physical Society, 53, pp ,

THE JOURNAL OF KOREAN INSTITUTE OF ELECTROMAGNETIC ENGINEERING AND SCIENCE Oct.; 27(10),

THE JOURNAL OF KOREAN INSTITUTE OF ELECTROMAGNETIC ENGINEERING AND SCIENCE. 2016 Oct.; 27(10), 926 934. http://dx.doi.org/10.5515/kjkiees.2016.27.10.926 ISSN 1226-3133 (Print) ISSN 2288-226X (Online) Multi-Function