• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.6
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• pp.479-487
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• 2020

A new double-pulse laser system that combines Raman and laser induced plasma spectroscopy (LIPS) in a single unit is proposed. The study attempts to enhance the laser induced plasma signals while simultaneously extracting the desired molecular signals from Raman spectroscopy. In low pressure conditions such as the lunar atmosphere, the measuring of plasma emission is hard because of the low electron density and short persistence time causing a rapid plasma expansion. Furthermore, in the integration of the detecting system aimed at space exploration, the minimization of laser system is important in terms of the payload mass. Simultaneous molecular and atomic detection that gave highly resolved spectral data at pressure below 0.07 torr is demonstrated amongst eight rock samples test. The plasma stacking produced from the double-pulse laser enhanced the signal intensity of calcium and oxygen lines in calcite matrix by twofold, compared to a conventional LIPS.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.608-611
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• 2011

Laser-induced combustions and explosions generated by high laser irradiances were explored by Laser-Induced Breakdown Spectroscopy (LIBS) in rich, and stoichiometric conditions. The laser used for target ablation is a Q-switched Nd:YAG laser with 7 ns pulse duration at wavelength of 1064 nm laser energies from 40 mJ to 2500 mJ ($6.88{\times}10^{10}-6.53{\times}10^{11}\;W/cm^2$). The plasma light source from aluminum detected by the echelle grating spectrometer and coupled to the gated ICCD(a resolution (${\lambda}/{\Delta}{\lambda}$) of 5000). This spectroscopic study has been investigated for obtaining both the atomic signals of aluminum (fuel) - oxygen (oxidizer) and the calculated ambient condition (plasma temperature and electron density). The essence of the paper is observing specific electron density ratio which can support the processes of combustion and explosion between ablated aluminum plume and oxygen from air by inducing high power laser.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.120.2-120.2
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• 2015

We propose a novel direct writing technique with a femtosecond laser enabling selective modification of not only the morphology of conducting polymer thin films but also the orientation and alignment of the polymer crystal. Surface relief gratings resulting from photoexpansion on P3HT:PCBM and PEDOT:PSS thin films were fabricated by femtosecond laser direct writing. The photoexpansion was induced at laser fluence below the ablation threshold of the thin film. The morphology (size and shape) of photoexpansion could be quantitatively controlled by laser writing parameters such as focused beam size, writing speed, and laser fluence. GIWAX results showed that face-on P3HT crystals were largely increased in the photoexpansion in comparison with pristine region of the thin film. In addition, the face-on P3HTs in the photoexpansion were aligned with their orientation along the polarization of the laser. The micro-RAMAN spectra confirmed that neither chemical composition change nor the polymer chain breaking was observable after femtosecond laser irradiation. We believe that this laser direct writing technique opens a new door to the fabrication of more efficient OPVs via non-contact, toxic-free approach.

• Proceedings of the Microbiological Society of Korea Conference
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• 2005.05a
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• pp.206.2-206
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• 2005

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05a
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• pp.172-175
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• 2002

The technique of induced discharge by a pulsed CO2 laser is being applied to control electrical discharge path, material processing, triggered lightning for protecting the power equipments. In this paper, we have investigated about the characteristics of the induced discharge at atmospheric conditions by using a plasma channel, which is produced when a pulsed CO2 laser radiation is focused by a focusing mirror as a trigger source. A plasma channel produced by laser radiation has an effect on decreasing the threshold voltage and inducing the discharge in both needle electrodes. We have confirmed a delay time between a produced plasma channel and an electrical discharge after laser radiation. We provided the decreased voltage lower than the natural discharge voltage between electrode type of needles and was induced the discharge by forming a plasma channel between them. In this research we could understand the time delay of induced discharge by laser radiation, and the characteristics of the discharge cause by the decrease in the threshold voltage, and the polarity effect by changes of plasma channel positions between two electrodes.

• Korean Journal of Acupuncture
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• v.29 no.1
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• pp.131-141
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• 2012

Objectives : This study was performed to investigate the effect of invasive laser acupuncture treatment at Liver Brook (LR2) acupoint and Liver Sea (LR8) acupoint on liver damage induced by D-galactosamine (D-GalN) in rats Methods : Liver damage was induced by D-GalN. The experimental rats were divided into two groups (control group, Low Level Laser Treatment (LLLT) group). Control groups were classified into small groups. Intact group had no liver damage and no treatment. D-GalN group was induced liver damage induced by D-GalN and not treated. LLLT group were induced liver damage induced by D-GalN and then treated at the LR2 or LR8 acupoint with 532, 658, 904 nm invasive laser acupuncture. The treatment was carried out three days at a time for 15days at both acupoints. To examine mechanism of the effect of invasive laser acupuncture, we measured the contents of ASP, ALT, ALP, TBIL in serum, CBC in blood and SOD in liver tissue. Results : The change of body weight increased in all groups. That change was AST and ALP, the AST activity decreased significantly compared with the control groups and decreased by 532 nm and 904 nm both LLLT groups. But ALP increased at LR8 acupoint by 658 nm. TBIL level significantly decreased in all LLLT groups. The SOD of LLLT groups increased in the liver tissue of rats compared to the control groups. SOD activity indicated that LLLT can help cellular defense mechanism by preventing scavenging hydrogen peroxide. In the change of WBC, it was increased in D-GalN Control group compared to intact group and LLLT groups. Conclusions : These results suggested that invasive laser acupuncture treatment at LR2 or LR8 acupoint reduced activation of hepatic enzyme and damage of liver tissue. Thus, the effect of invasive laser acupuncture was nearly identical to the way of the traditional acupuncture for the treatment of hepatocytotoxicity.

• Journal of Mechanical Science and Technology
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• v.15 no.9
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• pp.1311-1318
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• 2001

It is necessary to diagnose accurately the characteristics of soot formation and oxidation in a diesel engine. Whereas past measurement techniques for soot concentration give limited information for soot, laser-based two-dimensional imaging diagnostics have a potential to provide temporally and spatially superior resolved measurements of the soot distribution. The technique using laser sheet beam has been applied to an optically accessible diesel engine for the quantitative measurement of soot. The results provided the information for reduction of soot from the diesel engine. Both LIS (Laser Induced Scattering) and LII (Laser Induced Incandescence) techniques were used simultaneously in this study. The images of LIS and LII showed the quantitative distribution of the soot concentration in the diesel engine. In this study, several results were obtained by the simultaneous measurements of LIS and LII technique. The diameter and number density of soot in combustion chamber of the test engine were obtained from ATDC 20 degree to 110 degree. The soot diameter increased about 37% between ATDC 20 degree and 110 degree. The number density of soot, however, decreased significantly between ATDC 40 degree and 70 degree.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.570-571
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• 2005

In this paper, we introduced a LIF measurement method and summarized the theoretical side. When an altered wavelength of laser and electric power, lamp applied electric power, we measured the relative density of the metastable state in mercury after observing a laser induced fluorescence signal of 404.8nm and 546.2nm, and confirmed the horizontal distribution of plasma density in the discharge lamp. The results confirmed the resonance phenomenon regarding the energy level of atoms along a wavelength change, and also confirmed that the largest fluorescent signal in 436nm, and that the density of atoms in 546.2nm ($6^3S_1\rightarrow6^3P_2$) were larger than 404.8nm ($6^3S_1\rightarrow6^3P_1$). According to the increase of lamp applied electric power, plasma density increased, too. When increased with laser electric power, the L1F signal reached a saturation state in more than 2.6mJ. When partial plasma density distribution along a horizontal axis was measured using the laser induced fluorescence method, the density decreased by recombination away from the center.

• Journal of the Korean Society of Industry Convergence
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• v.23 no.4_2
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• pp.693-699
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• 2020

355nm UV pulse laser is irradiated on the surface of polyimide (PI) by LDW (Laser Direct Writing) method to produce a high sensitivity flexible humidity sensor using a simple one-step process. The LDW method continuously investigates 2-D CAD data using a galvano scanner and an F-lens. This method is non-contact, so it minimizes physical strain on the PI. Laser-induced graphene (LIG) produced by lasers has a high surface area due to its high flexibility and numerous pores and oxidizers compared to conductors. For this reason, it is highly useful as a flexible humidity sensor. The humidity sensor produced in this study was attached to the inside of a mask filter, which has become a hot topic recently, and its applicability was confirmed.The measurement of humidity measured the sensitivity, reactivity, stability and recovery behavior of the sensor by measuring changes in capacitance and resistance.

• Journal of the Korean Physical Society
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• v.73 no.9
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• pp.1279-1282
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• 2018

This paper reports the deposition of a metal line using a multilayer stack and laser-induced forward transfer (LIFT) using a low cost continuous wave blue laser with a wavelength of 450 nm. The donor structure was composed of a light-to-heat (LTH) layer, a release layer, and a transfer layer in series. Amorphous silicon as the LTH layer absorbs photon energy and converts it to heat. A release layer was melted so that a silver transfer layer would be transferred to the receiver substrate. The transferred silver layer showed reasonable physical and electrical characteristics. A low cost fine linewidth metal layer could be achieved using this modified LIFT technique and blue laser.