• Journal of Advanced Marine Engineering and Technology
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• v.20 no.5
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• pp.93-102
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• 1996

Laser-induced plume and laser-target interaction during pulsed laser deposition are demonstrated for a lead zirconate titanate (PZT). A KrF excimer laser (wavelength 248nm) was used and the laser was pulsed at 20Hz, with nominal pulse width of 20ns. The laser fluence was~$16J/cm^2,$ with 100mJ per pulse. The laser-induced plasma plume for nanosecond laser irradiation on PZT target has been investigated by optical emission spectra using an optical multichannel analyzer(OMA) and by direct observation of the plume using an ICCD high speed photography. OMA analysis showed two distinct ionic species with different expansion velocities of fast or slow according to their ionization states. The ion velocity of the front surface of the developing plume was about $10^7$cm/sec and corresponding kinetic energy was about 100eV. ICCD photograph showed another kind of even slower moving particles ejected from the target. These particles considered expelled molten parts of the target. SEM morphologies of the laser irradiated targets showed drastic melting and material removal by the laser pulse, and also showed the evidence of the molten particle ejection. The physics of the plasma(plume) formation and particle ejection has been discussed.

• Proceedings of the Optical Society of Korea Conference
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• 1991.06a
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• pp.64-64
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• 1991

The interaction of high-intensity, focused, nanosecond laser light with matter results in the production of high-temperature plasma, which in turn emits an intense pulse of x rays. The x-ray spectrum consists of strong line components of several keV photon energy and broad continuum. Such an x-ray source provides many advantages over conventional ones for many applications. Pulse nature of the x-ray emission is well-suited for studying transient phenomena and for imaging living biological specimen. Recent experiments have also shown that the laser plasma x ray may be used for x ray lithography. These studies and other applications will be discussed in detail.

• 한국정보디스플레이학회:학술대회논문집
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• 2000.01a
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• pp.21-22
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• 2000

Laser diagnostic method in a plasma display discharge cell was introduced. The information of electric field, potential and electron temperature et al. in the surface of plasma display panel can be measured using laser induced fluorescence spectroscopy. However, because of the very small discharge dimension of ${\sim}$ 100 ${\mu}m$, the measurement attempt has almost not been performed. In this paper, the direct measurement possibility of the parameters and the recent work of electric field measurement are demonstrated in the plasma display panel.

• Proceedings of the Optical Society of Korea Conference
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• 2003.02a
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• pp.42-43
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• 2003

The nonlinear three-wave interaction is an interesting topic having various applications in nonlinear optics, hydrodynamics, acoustic waves, and plasma physics. The resonant interaction between two laser pulses and a plasma wave plays important roles in plasma heating, laser reflection in the inertial confinement fusion (ICF), plasma wakefield generation, and ultra-intense laser pulse amplification and pulse compression using stimulated Raman backscattering (RBS). (omitted)

• Journal of Welding and Joining
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• v.31 no.4
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• pp.28-33
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• 2013

The effects of laser welding beam quality is very large. However, not an analysing case was found for the difference on the plasma emission signal during laser welding according to the beam quality. Therefore, in this study, we compared and evaluated penetration and signal change according to the beam quality at the a similar wavelength band by using a fiber laser and Nd:YAG laser. In addition, we took high speed videography in order to make sure that FFT analysis reflects the actual motion period of keyhole and found the period of video analysis and FFT mostly matched. As a result, it is expected to secure higher reliability than evaluating signal intensity when appling FFT to monitoring.

• Journal of Power System Engineering
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• v.4 no.4
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• pp.48-53
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• 2000

This study was aimed at observing the influence of laser irradiation on a $ZrO_2-8%Y_2O_3$ ceramic coating layer fabricated by plasma spraying. The $ZrO_2-8%Y_2O_3$ ceramic powder was plasma sprayed onto SS400 carbon steel substrate and laser irradiated on the coating layer under various conditions of laser power and beam diameters. As to the as-sprayed specimen and laser-treated specimen, a hardness test and a microstructure analysis were performed. Hardness was measured by a microhardness tester; microstructure was observed by an optical microscope and a scanning electron microscope. The result was that the microstructure of the laser-irradiated coating layer was dense; porosities almost disappeared and hardness increased. It was also observed that microcracks occured in the laser-irradiated coating layer.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.271-277
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• 2004

As one of the concepts of the laser/electric hybrid propulsion system, a feasibility study on possibilities of electrostatic acceleration of a laser ablation plasma induced from a solid target was conducted. Energy distributions of accelerated ions were measured by a Faraday cup. A time-of-flight measurement was also conducted for ion velocity measurement. It was found that an average speed of ions from a pure laser ablation in this case was about 20 km/sec for pulse energy of 40 $\mu$J/pulse with pulse width of 250 psec. On the other hand, through an electrostatic field with a + I ,000 V electrode, the speed could be accelerated up to 40 km/sec. It was shown that the electrode with positive potential was more effective than that with negative potential for positive-ion acceleration in laser induced plasma, or pulsed plasma, in which ions were induced with the Coulomb explosion following electrons. In addition, the ion-acceleration or deceleration strongly depended on conditions of pairs of inner diameter and electrodes gap.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.320-324
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• 2004

Laser Propulsion is a device that generates thrust using laser energy. Laser-driven In-Tube Accelerator (LITA) has been developed at Tohoku University. LITA is a laser propulsion system that accelerates an object not in an open air but in a tube. Experiments of vertical launching and pressure measurement on the tube wall were carried out and in order to observe the initial state of plasma and blast wave, the visualization experiment was carried out using the shadowgraph method. In this study, the time variation of pressure on the tube wall is numerically simulated solving Euler equation. In order to model the laser energy, heat source function added to the frozen flow Euler equation. Plasma size from the shadowgraph images was used for the initial condition of laser energy input. For verification of the modeling, these results were compared with the previous experimental and numerical results. From these verifications, an analysis of LITA performance will be investigated.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2001.10a
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• pp.292-300
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• 2001

The paper describes spectroscopic characteristics of plasma induces in the pulsed YAG laser welding of alloys containing a large amount of volatile elements. The authors have conducted the spectroscopic analyses of laser induced Al-Mg alloys plasma in the air and argon atmosphere. In the air environment, the identified spectra were atomic lines of Al, Mg, Cr, Mn, Cu, Fe and Zn, and singly ionized Mg lines, as well as the intense molecular spectra of A10 and Mg0 formed by chemical reactions of evaporated Al and Mg atoms from the pool surface with oxygen in the air. In argon atmosphere, Mg0 and AI0 spectra vanished, but AIH spectrum was detected. The hydrogen source was presumably hydrogen dissolved in the base metals, water absorbed on the surface oxide layer, or $H_2$ and $H_2O$ in the shielding gas. The resonant 1ines of Al and Mg were strongly self-absorbed, in particular, self-absorption of the Mg 1ine was predominant. These results show that the laser induced plasma was made of metal1ic vapor with relatively low temperature and high density.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.6
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• pp.551-557
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• 2002

Carbon nitride films have been deposited on Si(100) substrate by a high voltage discharge plasma combined with laser ablation in a nitrogen atmosphere. The films were grown both with the without the presence of an assisting focused Nd:YAG laser ablation. The laser ablation of the graphite target leads to vapor plume plasma expending into th ambient nitrogen arc discharge area. X-ray photoelectron spectroscopy and Auger electron spectroscopy were used to identify the binding structure and the content of the nitrogen species in the deposited films. The nitrogen content of the films was found to increase drastically with an increase of nitrogen pressure. The surface morphology of the films was studied using a scanning electron microscopy. Data of infrared spectroscopy and x-ray photoelectron spectroscopy indicate the existence of carbon-nitrogen bonds in the films. The x-ray diffraction measurements have also been taken to characterize the crystal properties of the obtained films.