• Korean Journal of Optics and Photonics
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• v.4 no.1
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• pp.47-56
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• 1993

Practical efficiencies of pulsed gas discharge lasers utilizing vaporized Au, Ba, Cu, Fe, Mn, Pb, TI atoms are numerically optimized for a discharge pulse of 30 ns rise time at 5 kHz pulse repetition rate. Calculated optimum operating temperatures are close to the values at which the vapor pressure of each atom is about 1 Torr and are in good agreement with experimental values reported elasewhere. The optimum charging voltage was about 4 kV for all atomic vapor lasers except the TI laser. The calculated maximum efficiencies that have been discussed for possible limiting efficiencies for each laser were considerably higher than the reported experimental values. Especially, they were as high as 6.8% for Mn laser and 15% for Ba laser that were comparable to the 8.5% of copper vapor laser, from which considerably higher efficiencies can be expected for these two lasers experimentally. But, the present calculation shows a very low efficiency of 0.058% and requires an exceptional operating condition for the TI laser.

• Korean Journal of Optics and Photonics
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• v.1 no.2
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• pp.155-161
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• 1990

A Continous wave tunable $CO_2$ laser which is the slow axial flow type was construccted for the optical pumping of methyl alcohol ($CH_3OH$) laser. The reflective grating of 100 grooveslmm and 10.6$\mu\textrm{m}$ blaze wavelength was used to select wavelength. We have investigated continous outpu: power characteristics, and then have compared tuned output power profile with the gain curve of $CO_2$ laser. The optimum condition for maxium power was found at the gas mixing ratio 1 : 3 : 10 for $CO_2: N_2$ and He. under this condition the flow rate, pressure of lasing gas and discharge current are 9.5 llmin. 14 torr, and 55 mA respectively. The maxium output power was 55 Wlm. Output power of single wavelength operation was measured on 60 individual rotation vibration transitions in the P and K branches of the 9.5$\mu\textrm{m}$ band and 10.4$\mu\textrm{m}$ band in $CO_2$. The output power profile obtained from each band is well consistent with the gain curve of $CO_2$ laser and maxium tuned output power was 20 watt.

• Proceedings of the KWS Conference
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• 2000.10a
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• pp.81-83
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• 2000

• Proceedings of the KWS Conference
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• 1994.10a
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• pp.27-28
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• 1994

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.285-288
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• 2009

In order to understand spray characteristics with inflowing air from the compressor in the APU gas turbine combustor, we performed spray visualization test by using ND-Yag Laser sheet beam. The sector combustor which size is 1/6 of the real combustor was manufactured. Turbo blower is used as an air supplying device to simulate gas turbine air flow condition. In the case of 75 m/s combustor inlet air flow condition, spray angle way increased and dispersed widely than without airflow condition.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07b
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• pp.1218-1220
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• 2005

We have developed laser absorption spectroscopy system for the measurement of excited Xe atoms in micro-discharged AC-PDP plasma. In this study, we have measured the absorption signals for the $1S_5$ xenon metastable state in the PDP cell with the various gas mixtures of Ne-Xe(1%), Ne-Xe(4%) and Ne-Xe(10%) under fixed gas pressure of 350 Torr and the eletrode gap distance of 50um. It is found that the maximum excited xenon densities are $1.2^{\ast}10^{12}\;cm^{-3}$, $1.8^{\ast}10^{12}\;cm^{-3}$ and $2.7^{\ast}10^{12}cm^{-3}$ for gas mixtures of Ne-Xe(1%), Ne-Xe(4%) and Ne-Xe(10%) respectively, in this experiment.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.6
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• pp.773-782
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• 2016

The performance of the CT-TDLAS (computed tomography-tunable diode laser absorption spectroscopy) is strongly dependent upon the line broadening functions. The line of the laser beam used in the TDLAS is scattered by the natural broadening, the collisional broadening and the doppler broadening. The influence of the natural broadening to the experimental spectra obtained in the TDLAS is negligible. The influences of the collisional broadening and the doppler broadening to the experimental spectra are relatively large, in high pressure gas flows and in high temperature low pressure gas flows, respectively. In this study, optimal coefficients are proposed for the doppler broadening function by using the experimental data obtained in a flat burner test. The optimal coefficients were ${\gamma}_j=0.16$ and n=0.37. Using these coefficients, the temperature and concentration distributions at the engine exhaust gas pipe have been calculated showing their validities.

• Journal of Welding and Joining
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• v.35 no.1
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• pp.68-73
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• 2017

During welding of Ni based superalloy, hot cracking was usually happen in the fusion zone of a weld. In this study, the laser weldability of Inconel 713C alloy for the turbocharger wastegate valve (WGV) was evaluated with various welding conditions, such as laser power, welding speed, shielding gas. Welding conditions were optimized by bead-on-plate (BOP) and butt joint welding. For the evaluation of laser weldability, bead shapes and weld microstructures were investigated and tensile test was conducted. The fracture surfaces were investigated for the understanding the cause of the fracture.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.362-364
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• 2001

The pulsed laser deposition(PLD) technology was used for the deposition of phosphor substance, Gd$_2$O$_3$on commercial glass. An Nd:YAG laser was employed for the deposition (wavelength 266nm, energy up to 100mJ/pu1se, pulse duration is 5ns and repetition rate 10 Hz). With respect to films grown by conventional PLD, this study exhibited the condition at normal temperature. Experiments were done without any reactive gas at a pressure of 10$^{-5}$ ~10$^{-6}$ Torr using second harmonic(λ=532 nm) and fourth harmonic(λ=266 nm) Nd:YAG laser. Analyses of the deposited material grown are performed by EDX, AFM, SEM, PL meseurements.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.366-370
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• 1997

This paper descibes a micro groove machining process on the polyurethane biopolymer by KrF excimer laser. To investigate the etch charcteristics of polyurethane biopolymer quantitatively,laser system for ablation was installed with high precison moter and then polymer ablation experiment, in which paramteters were fluence,pulse repetition rate,numbers of pulses and assist gas, was carred out. In this experiment, we found out that the value of critical energy density for ablation is 30mJ/cmsup2/ and the etching rate is more dependent on the pulse number and fluence than any other pamameter. Finally, we machined micro grooves for fiexibility as width 300.mu.m depth 100.mu.m and port for micro-devices mounting as length 100.mu.m width 300.mu.m depth .mu.m on the outer wallof polyurethane biopolymer tube which is used as medical device.