• Journal of Magnetics
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• 제18권2호
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• pp.86-89
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• 2013

This paper shows a new effective approach to measure crystallization temperature of soft magnetic underlayer (SUL) for next generation of heat assisted perpendicular recording media. This approach uses temperature dependent reflectivity, which shows a clear jump when samples are crystallized. To achieve this measurement, an optical system is set up using hot plate and infrared laser. Reflectivity of SUL $(Co_{70}Fe_{30})_{92}Ta_3Zr_5$ shows a clear jump at its amorphous-crystalline transition temperature. Experiment results show this effect is clear in infrared region, and is weak for visible light.

• 대한기계학회논문집A
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• 제31권4호
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• pp.483-489
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• 2007

We have investigated quantitative measurement techniques of the degree of dispersion of single-walled carbon nanotubes (SWNTs). SWNTs were suspended in aqueous media using a sodium dodecyl sulfate (SDS) surfactant. SWNTs with different dispersion states were prepared by controlling the intensity and time of sonication and centrifugation. The laser spectroscopic techniques were employed to characterize the dispersion state; i.e., raman fluorescence and absorption spectroscopic techniques. Raman spectroscopy has been used to probe the dispersion and aggregation state of SWNTs in solution. Individually suspended SWNTs show increased fluorescence peaks and decreased roping peaks at a raman shift 267 $cm^{-1}$ compared with the samples containing bundles of SWNTs. The ultraviolet-visible-near infrared (UV-vis-NIR) absorption spectrum of decanted supernatant samples show sharp van Hove singularity peaks

• KIEE International Transactions on Electrophysics and Applications
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• 제11C권3호
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• pp.75-80
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• 2001

Holographic polymer dispersed liquid crystals (HPDLCs) have fabricated by irradiating an Ar-ion laser ( ${\lambda}$=514nm) at various intensity on LC/acrylate monomer mixtures which were sandwitched between two ITO coated glass plates. Monomer systems were composed of dipentaerythritol-hydroxy penta acrylate (DPHPA, f=5)/monofunctional acrylate monofunctional monomers. The LC used in this system was E7 (BL001, Merck). Gratings were fabricated by periodic interference of twobeams. Reflection efficiency-irradiation intensity-monomer type relationships were obtained from the UV-visible spectra of the HPDLC films. Peaks were found at a bit smaller wavelength than 514nm, due to the shrinkage of mixture volume upon polymerization. Real time measurements of diffraction efficiency have been obtained according to monomer types and LC contents.

• KIEE International Transactions on Electrophysics and Applications
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• 제11C권3호
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• pp.91-95
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• 2001

Reflective holographic polymer dispersed liquid crystal(HPDLC) device has a multilayer structure consisting of alternate layers of polymer and liquid crystal droplets. Periodic modulation of a refractive index reflects light of a specific wavelength in accordance with Braggs law. Samples cured isotropically were illuminated with an Argon-ion lase at 514nm. We optimized the reflcetion efficiency of HPDLC as a function of monomer functionality, LC composition and irradiation intensity. The properties of the HPDLC films were observed by UV-visible spectroscopy. We found that the maximum reflection efficiency depends on the monomer functionality, LC composition, and laser intensity. We expect these films could be used in full-color reflective display by stacking them to obtain a mixture of colors.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.242-243
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• 2007

Highly transparent conducting aluminum-doped zinc oxide (AZO) thin films were deposited on Corning glass substrate using an Nd:YAG pulsed laser deposition technology. AZO thin films deposited with 650nm thickness showed the best electrical properties of the electrical resistivity of $4.6{\times}10^{-4}[{\Omega}{\cdot}cm]$, a carrier concentration of $9.3{\times}10^{20}[cm^{-3}]$, and a carrier mobility of $31[cm^2/V{\cdot}s]$. Besides, the optical transmittance spectra in visible region (200-800nm) of AZO thin films show an high average transmittance over 90%.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.1349-1350
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• 2007

Epitaxial thin films of aluminum-doped zinc oxide (AZO) have been deposited on commercial corning glass using an Nd:YAG pulsed laser deposition technology. The structural, electrical and optical properties of these films were investigated as a function of oxygen pressure. The experimental results show that the electrical resistivity of films deposited at 5 mTorr with substrate temperature of $300^{\circ}C$ were $4.633{\times}10^{-4}$. The average transmission of AZO thin films in the visible range were over 90%.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.211.1-211.1
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• 2013

We fabricate the conductive zinc oxide(ZnO) thin film using UV-enhanced atomic layer deposition. ZnO is semiconductor with a wide band gap(3.37eV) and transparent in the visible region. ZnO can be deposited with various method, such as metal organic chemical vapour deposition, magnetron sputtering and pulsed laser ablation deposition. In this experiment, ZnO thin films was deposited by atomic layer deposition using diethylzinc (DEZ) and D.I water as precursors with UV irradiation during water dosing. As a function of UV exposure time, the resistivity of ZnO thin films decreased dramatically. We were able to confirm that UV irradiation is one of the effective way to improve conductivity of ZnO thin film. The resistivity was investigated by 4 point probe. Additionally, we confirm the thin film composition is ZnO by X-ray photoelectron spectroscopy. We anticipate that this UV-enhanced ZnO thin film can be applied to electronics or photonic devices as transparent electrode.

• Bulletin of the Korean Chemical Society
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• 제17권7호
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• pp.607-612
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• 1996

A series of new NLO-active poly(4-nitrophenylallylamine) derivatives was synthesized by the nucleophilic substitution reaction of several substituted 4-nitrohalobenzenes and poly(allylamine hydrochloride). All polymers obtained were amorphous and their glass transition temperatures (Tg) were observed around 148-160 ℃. For each of these polymers, their specific Tg values were dependent on characteristic electronic structures. UV-visible absorption spectra showed maximum absorption intensity at 355-393 nm for π-π* transition of alkylaminonitrophenyl groups. The χ(2)value of poly(4-nitrophenylallylamine), as determined by the second harmonic generation at 1064 nm, for a thin polymer film poled at an elevated temperature, was 1.4x10-8esu. The third-order NLO properties of poly(4-nitrophenylallylamine) derivatives were evaluated through measurement of degenerate four-wave mixing technique and χ(3) coefficient in the range of 2.7~3.2x10-12 esu at 602 nm was found with 400 fs laser pulses.

• 한국광학회지
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• 제31권3호
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• pp.142-147
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• 2020

본 연구에서는 Yb 광섬유 레이저 MOPA (master oscillator power amplifier) 시스템을 구축하여 고출력, 고효율의 근적외선 레이저 빔을 발진시키고, 이를 주기분극반전 준위상정합 비선형 광학 소자인 MgO:PPSLT에 단일 통과시키는 방식을 통하여 고출력 고효율 연속발진 녹색 레이저 빔을 생성하는 방법을 보고한다. 자발 펄싱을 억제할 수 있는 패브리-패롯 피드백 공진기 구조를 사용한 광섬유 레이저 주공진기를 사용하여 선폭이 좁고 선형 편광된 1064 nm 레이저 씨앗 빔을 안정적으로 생성할 수 있었으며, 이를 Yb 광섬유 증폭단에서 고출력으로 증폭시켰다. 증폭된 레이저 빔을 MgO:PPSLT에 통과시켜 고출력 고효율의 이차조화파를 얻을 수 있었는데, 이때 얻은 532 nm 레이저의 최고 출력은 기본 입사광의 출력이 25.0 W일 때 11.1 W였으며, 변환 효율은 44.4%를 얻었다.

• 한국의학물리학회지:의학물리
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• 제16권2호
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• pp.104-109
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• 2005

암치료에 사용되고 있는 광역학 치료는 환자에게 광민감제를 투여하고 다이오드 레이저(630 nm)를 조사하여 생성되는 단일상태 산소와 자유 라디칼에 의해 암조직을 괴사시키는 치료방법이다. 현재 광역학 치료의 문제점은 부피가 큰 종양이나 고형암에서는 빛이 종양전체를 투과할 수 없으므로 광역학 치료의 효과가 떨어지는 것이다. 따라서 이 문제를 해결하기 위하여 간질성 광역학 치료법을 개발하고자 한다. 생체조직내의 정확한 광선량 측정이 간질성광역학치료의 효과에 매우 중요한 영향을 주므로, 실험 연구에 사용된 계수는 실제 생체조직의 광학 계수이다. 생체조직 대부분은 가시광선영역에서 큰 산란계수를 가지며, 투과 깊이에 많은 영향을 미치는 것으로 확인되었다. 가시영역에서의 인체조직의 투과깊이는 약 $15\~20mm$이었다. 몬테칼로 시뮬레이션(Monte Carlo simulation)을 이용하여 생체조직내의 광전파, 광선량, 에너지율, 투과깊이를 잘 측정할 수 있음을 알았다. 그리고 이 시뮬레이션 결과를 가지고 고형암에 간질성 광역학 치료를 하여 치료효과를 확인하였다.