• Korean Journal of Materials Research
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• v.11 no.9
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• pp.792-796
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• 2001

For electron beam lithography and SEM(scanning electron microscopy) applications, miniaturized electrostatic lenses called a microcolumn have been fabricated. In this paper, we report the fabrication technique for 20~30$\mu\textrm{m}$ apertures of electron lenses based on silicon and Mo membrane using an active Q-switched Nd:YAG laser. Experimental conditions of laser micromachining for silicon and Mo membrane are improved. The geometrical structures, such as the diameter and the preciseness of the micron-size aperture are dependent upon the total energy of the laser pulse train, laser pulse width, and the diameter of laser spot.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.340-343
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• 2000

ITO(Indium Tin Oxide) films for transparent electrodes of FPD(Flat Panel Display) were patterned in atmosphere using laser. A pulse type(repetition rate of 10 Hz) Q-switched Nd:YAG laser which can generate the fundamental wavelength at 1064 nm or its harmonics(532, 266 nm) was used for Patterning of the ITO film. In case of using the second harmonic(532 nm) of Nd:YAG laser, the ITO film(thickness of 20 nm) was removed clearly with a laser fluence of 5.2 J/$\textrm{cm}^2$ and a beam scan speed of 200${\mu}{\textrm}{m}$/s. But the glass substrate was damaged when the laser fluence was over 5.2 J/$\textrm{cm}^2$. We discussed the etching mechanism of the ITO film using Nd:YAG laser with observation of the etching characteristics including a depths and widths of ITO films as a function of laser fluence using SEM(Scanning Electron Microscopy) and surface profiler($\alpha$-step 500).

• Korean Journal of Optics and Photonics
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• v.8 no.5
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• pp.357-361
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• 1997

We report the operation of a self-starting phase conjugate laser(PCL) oscillator which compensates intracavity phase distortion. The self-starting PCL in the population inverted Nd:YAG gain media produced an output energy of 200 mJ in a 20 ns single-longitudinal-mode pulse at 10Hz. And it showed well-defined Gaussian spatial profile.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.176-177
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• 2005

PDMS는 생명공학 분야에서 중요한 기술적 폴리머이다. Nd:YAG레이저의 4고조파 ($\lambda$=266nm, pulse) 레이저를 사용하여 표면 처리를 하여 PDMS 표면의 습윤성과 접착성의 향상됨을 확인하였다. 식각한 PDMS는 샘물체의 미세회로에 사용될 수 있다. 본 논문은 레이저 빔의 주사속도를 변화시키며 PDMS를 레이저로 식각하며 PDMS의 식각 특성을 연구한다 식각 특성을 의존성이 가장 효과적인 주사 속도에 대한 의존성을 규명하고자 스테이지 컨트롤러의 속도를 변화시키며 실험하였다. 그리고 최적의 레이저 출력값을 알아내려고 레이저 출력값을 조절하며 실험 하였다. 단차측정기(알파스템)을 이용하여 식각형상과 식각 효율 등을 분석하였다.

• Journal of the Korean Institute of Telematics and Electronics
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• v.21 no.1
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• pp.38-44
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• 1984

Subnanosecond optical pulses with 0.8-1.Bum wavelength are generated by experimentally realizing a single pass fiber Raman laser. This fiber Raman laser is pumped by a mode-locked and Q-switched Nd-YAG laser. Two wave sum frequency phenomenon is also obsenred in the course of the experimental work. The fiber Raman laser is then used to measure dispersion characteristics of a sin\ulcorner mode fiber in the long-wavelength lesion.

• Proceedings of the KIEE Conference
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• 1993.07a
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• pp.460-463
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• 1993

In this paper, The laser transmitter module is designed as the subsystem of the high repetitive laser rangefinder. The module consists of high voltage power supply, high voltage control circuits, high voltage discharger, electro-optic Q-switch driver, and laser resonator. The high voltage power supply is composed of 2-phase flyback converter. And it has 220W power level and 78% conversion efficiency. From the Q-switch driver of the crossed porro resonator, the phase retardation voltage is switched from 600V to -1500V with 200ns falling time. The module can be operated up to 15Hz. And it generates the laser pulse which has 20ns width and 80mJ.

• Korean Journal of Optics and Photonics
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• v.13 no.4
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• pp.340-346
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• 2002

To understand the characteristics of the passively Q-switched Nd:YAG laser output energy with $Cr^{4+}$:YAG saturable absorbers, the transmissions of $Cr^{4+}$:YAG and the inversion population densities of Nd:YAG at the onset of Q-switch were experimentally analysed. The measured transmissions at the onset of Q-switch were 0.70$\pm$0.02 and 0.62$\pm$0.02 for the 0.48 and 0.38 of initial transmission, respectively. It means that the initial transmission loss of $Cr^{4+}$:YAG absorber is reduced in a low Q-state due to the initial absorbing effect of $Cr^{4+}$:YAG. In pumping stage, $Cr^{4+}$:YAG has absorbing processes due to the fluorescence and amplified spontaneous emissions of the Nd:YAG even if there is no laser oscillation. The minimum population inversion densities for Qswitch were approximately 3.7${\times}{10^{17}}$ and 4.0${\times}{10^{17}}$ $cm^{-3}$, respectively. At the beginning of Q-switch, the number density of $Cr^{4+}$ions in the ground state of $Cr^{4+}$:YAG was approximately 1.4${\times}{10^{17}}$ $cm^{-3}$ and the ratio of the ground to the excited state of absorbing $Cr^{4+}$ions was 0.44 both. The modified theoretical output energies with the initial absorbing effect were 18 and 18.5 mJ. The measured output energies were 17$\pm$1 and 18$\pm$1.5 mJ, respectively. The quantum extraction efficiencies of Q-switch were 0.32 both. The theoretical Q-switched output results with the initial absorbing effect of the saturable absorber are a good agreement with the experimental results.

• Korean Journal of Optics and Photonics
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• v.11 no.5
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• pp.365-370
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• 2000

We have constructed a collinear four pass Ti.sapphire laser amplifier by usmg polmization effect When we pumped the mnplifier with 188 mJ second harmonics of Q-switched Nd:YAG laser, we observed that a 450 mW 1l1cident cw Ti:sapphire laser beam is amphfled to pulse with energy of 34 mJ and pulse width (FWffM) of 25 os. We could mmllmze the a.mplified spontaneous emission by simple method of rotating the Tbapphire amplifier rod er rod

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.193-197
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• 2008

Array of micro-dimple on polyoxymethylene (POM) surface was fabricated using Q-switched Nd:YAG laser and its characteristics were studied in terms of heat affected zone (HAZ), dimple geometry, and the effect of specimen surface roughness. Process parameters such as lamp current, process time, and the stream of air in order to minimize HAZ and flow of molten polymer into cavity were extensively studied in this work. Dimple geometry was further investigated by 3-D optical microscopy to provide deep insight into morphological analysis near the dimples. This paper also presents the applicapability of micro-dimples in polymeric tribological system, such as a thrust bearing. Micro-dimples were expected to provide low coefficient of friction and enhanced lubricity at the sliding interface.

• Laser Solutions
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• v.1 no.1
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• pp.39-44
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• 1998

Laser ablation system for microscopic defect in thin film pattern was developed in this study. For the varification of this study, several laser ablation tests were accomplished. The ablated shape of thin film and the surface of base glass were analyzed by use of microscopic tools and EPMA. After some tests of thin film, the specification of laser and optical unit(max. laser energy is 25mJ, wavelength is 532nm, Q-switched Nd-YAG laser, frequency is 20Hz, Auto-focus unit is LD type.)