• 한국광학회지
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• 제21권6호
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• pp.254-258
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• 2010

타원형 모양의 모드 형태를 갖는 펄스형 레이저 다이오드 (laser diode)의 펄스 형태를 유지하면서 단일 모드 및 Gaussian 형태로 광 모드 변환을 유도하고 광출력을 증폭할 수 있는 기술에 대해서 연구하였다. 실험에서 사용한 펼스형 레이저 다이오드의 구경이 가로는 $300{\mu}m$이며, 세로는 $2{\mu}m$이고 출력은 $1.1mW/cm^2$이다. 렌즈형 광섬유를 사용하여 광결합을 유도하여 단일 모드 및 Gaussian 형태의 출력으로 변환시켰다. 그러나, 다중모드의 펄스형 레이저 다이오드의 출력을 단일모드 렌즈형 광섬유에 결합시키면 출력이 급격하게 감소한다. 따라서 master oscillator power amplifier (MOPA) 기반의 광증폭 기술을 이용하여 레이저 다이오드의 광출력을 증폭시켰다. 증폭 후에도 펄스 성질은 그대로 유지되었고, MOPA구조를 지나 증폭된 광 출력은 $29mW/cm^2$로 측정되었다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 추계학술대회 논문집 Vol.18
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• pp.11-12
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• 2005

[ $Pb(Zr_{0.48}Ti_{0.52})O_3$ ] (PZT) thin films were deposited on Pt(111)/Ti/$SiO_2$/Si substrates by pulsed laser deposition. In order to study the effect of different laser pulse repetition rate on the dielectric and ferroelectric properties of PZT thin films,2 Hz and 5 Hz of laser pulse repetition rate were selected. We compared the results of XRD pattern, dielectric constant and hysteresis characteristics. From the experimental data, we found that the electrical properties of PZT thin films which grown ar 2 Hz of laser pulse repetition rate were better than those which grown at 5 Hz of laser pulse repetition rate.

• 한국레이저가공학회지
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• 제5권2호
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• pp.31-38
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• 2002

This paper describes the process of nanoparticle synthesis by laser ablation of consolidated microparticles. We have generated nanoparticles by high-power pulsed laser ablation of Al, Cu and Ag microparticles using a Q-switched Nd:YAG laser (wavelength 355 nm, FWHM 5 ㎱, fluence 0.8∼2.0 J/㎠). Microparticles of mean diameter 18∼80 ㎛ are ablated in the ambient air The generated nanoparticles are collected on a glass substrate and the size distribution and morphology are examined using a scanning electron microscope and a transmission electron microscope. The effect of laser fluence and collector position on the distribution of particle size is investigated. The dynamics of ablation plume and shock wave is analyzed by monitoring the photoacoustic probe-beam deflection signal. Nanosecond time-resolved images of the ablation process are also obtained by laser flash shadowgraphy. Based on the experimental results, discussions are made on the dynamics of ablation plume.

• Bulletin of the Korean Chemical Society
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• 제13권5호
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• pp.553-556
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• 1992

The ${CO}_2$ laser absorption measurement of ${CH}_3{CH}_2Br$ utilizing photoacoustic (PA) technique was performed using a cw and a pulsed ${CO}_2$ lasers. The absorption profile in the ${CO}_2$ laser wavelength region (9-10 ${\mu}$m) and the macroscopic small signal absorption cross section at 10P(20) (10.59 ${\mu}$m, 944 $cm^{-1}$) laser line were measured using a cw ${CO}_2$ laser. The laser fluence dependence on infrared multiphoton absorption (IRMPA) was also studied with a pulsed TEA ${CO}_2$ laser at 10P(20) laser line. In view of monotonic increase of PA signal with the rise of laser fluence, it was suggested that the anharmonicity in pumped vibration mode did not restrict ir multiphoton absorption in ${CH}_3{CH}_2Br$ system as found in large molecular system.

• 한국전기전자재료학회논문지
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• 제11권2호
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• pp.133-137
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• 1998

$(Pb_{0.72}La_{0.28})Ti_{0.93}O_3(PLT(28))$ thin films were fabricated by pulsed laser deposition. PLT films deposited on $Pt/Ti/SiO_2/Si$ at $600^{\circ}C$ had a preferred orientation in (111) plane and at $550^{\circ}C$ had a (100) preferred orientation. We found that (111) preferred oriented films had well grown normal to substrate surface. This PLT(28) thin films of $1{\mu}m$ thickness had dielectric properties of ${\varepsilon}_r$=1300, dielectric $loss{\fallingdotseq}0.03 $. and had charge storage density of 10 [${\mu}C/cm^2$] and leakage current density of less than $10^{-6}[A/cm^2]$ at 100[kV/cm]. These results indicated that the PLT(28) thin films fabricated by pulsed laser deposition are suitable for DRAM capacitor application.

• 대한후두음성언어의학회지
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• 제19권1호
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• pp.54-57
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• 2008

Non-visualization of larynx is one of the reasons for failure of vocal fold surgery. Many otorhinolaryngologists may have a trouble in choice of alternative treatment if they experience this situation. The laryngeal mask airway could be alternative approach for this situation. We report a glottal papillomatous patient who was treated by pulsed dye laser via laryngeal mask airway after failure of vocal fold surgery via endotracheal intubation. The patient was a 73-year-old man. Laryngoscopy revealed a severe diffuse papillomatous lesion on right true vocal cord, anterior commissure, and partial left true vocal cord. The patient was refered for difficult laryngeal exposure during laryngomicrosurgey under general endotracheal anesthesia.

• Journal of Welding and Joining
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• 제31권2호
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• pp.57-62
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• 2013

Magnesium has good castability and limited workability, so its products have been manufactured by almost casting processes. In this study, a pulsed Nd:YAG laser was used to butt-weld the sand casting magnesium alloys. And the effect of welding conditions such as peak power, pulse width, welding speed was evaluated in detail. As a result of this study, large underfill and plenty of spatter taken place under the conditions with high peak power. Thus, it is recommended to use low peak power and long pulse width to obtain good welds with deep penetration. It is also confirmed that the welding speed and pps(pulse per second) are directly connected at weld defects such as underfill, porosity.

• 한국전기전자재료학회논문지
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• 제26권1호
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• pp.64-67
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• 2013

$Fe_3O_4$(magnetite) having half metallic property attracts great attention material with high curie temperature in spintronics. $Fe_3O_4$ thin films and nanowires were grown onto c-$Al_2O_3$(0001) at various substrate temperatures. $Fe_3O_4$ films deposited from 300 to $600^{\circ}C$ are influenced by thermal stress induced from mismatch of thermal expansion coefficient between $Fe_3O_4$ and $Al_2O_3$ (0001) substrate. The $Fe_3O_4$ nanowires grown at $640^{\circ}C$ showed a diameter of 130 nm and a length of $2-10{\mu}m$. The nanowire arrays fabricated by pulsed laser deposition technique have high coercivity($H_c$) of 608 Oe and Squareness($M_r/M_s$) of 0.68 in perpendicular direction.

• 대한금속재료학회지
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• 제50권5호
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• pp.395-400
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• 2012

In this study, we have investigated the surface morphology of hydroxyapatite (HA) coated Ti alloy surface using pulsed laser plating. The HA (tooth ash) films were grown by pulsed KrF excimer laser, film surfaces were analyzed for topology, chemical composition, crystal structure and electrochemical behavior. The Ti-6Al-4V alloy showed ${\alpha}$ and ${\beta}$ phase, Cp-Ti showed ${\alpha}$ phase and the HA coated surface showed HA and Ti alloy peaks. The HA coating layer was formed with $1-2{\mu}m$ droplets and grain-like particles, particles which were smaller than the HA target particle, and the composition of the HA coatings were composed of Ca and P. From the electrochemical test, the pitting potential (1580 mV) of HA coated Ti-6Al-4V alloy was higher than those of Cp-Ti (1060 mV) and HA coated Cp-Ti (1350 mV). The HA coated samples showed a lower current density than non-HA coated samples, whereas, the polarization resistance of HA coated samples showed a high value compared to non-HA coated samples.

• 한국레이저가공학회:학술대회논문집
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• 한국레이저가공학회 2002년도 추계학술발표대회 논문개요집
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• pp.105-108
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• 2002