• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.709-713
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• 2004

Characteristics of laser-assisted wet etching of titanium in phosphoric acid were investigated to examine the feasibility of this method for fabrication of high aspect ratio microchannels. Laser power, number of scans, etchant concentration, position of beam waist and scanning speed were taken into consideration as the major process parameters exerting the temperature distribution and the cross sectional profile of etched channels. Experimental results indicated that laser power influences on both etch width and depth while number of scans and scanning speed mainly affect on the etch depth. At a low etchant concentration, the cross sectional profile of an etched channel becomes a U-shape but it gradually turns into a V-shape as the concentration increases. On the other hand, surface of the laser beam focus with respect to the sample surface is found to be a key factor determining the bubble dynamics and thus the process stability. It is demonstrated that metallic microchannels with different cross sectional profiles can be fabricated by properly controlling the process parameters. Microchannels of aspect ratio up to 8 with the width and depth ranges of 8∼32 m and 50∼300 m, respectively, were fabricated.

• Korean Journal of Materials Research
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• v.7 no.3
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• pp.213-217
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• 1997

AOhf(Hcousto-r)l)tic niodulator) with :!OOlIiz freclucncl- and Sfi(;(Seconrl harmonic generation) green lasel-Lvith 53% nm wavelength were used for Il\'IIII~Dii.it,ii v~ilco disk recorder) FOI rhe appli~aptin of high densit]. optical recording, a high po\ver I ~ c r is r c ~ ~ l i ~ i l - u l ic I !tic. s\-sti,m a n d optic.,~I io;iting l,t)c>rs of each optical device must have a high laser damage threshoid hie rn;itie ant] retlwtive coatings on a $TeO_{2}$ singlc crystal. which is used as an acoustooptic material, by E-beam evaporation method. Laser damage threshold \vas nicdsureci hy Ar laser with the input power oi 0.55LV 1,aser damage threiholti 01 $ZrO_{2}$ and $SiO_{2}$. filn-is were higher than $AI_{2}O_{3}$ f i l m U'e also investigated a long--tern1 stability of the output po\ver of St{(; green laser

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.1019-1022
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• 2004

High performance p-ch poly-Si TFTs with excellent stability were developed. By using a frequency doubled DPSS CW laser, the a-Si on glass could be crystallized into one dimensional single crystalline silicon named as a sequential lateral crystallization (SLC) region. We fabricated p-ch TFTs on SLC region and the typical characteristic values of the TFTs were $u_{fe}$ = 180 $cm^2$/Vs, $V_{th}$ = -3 V, S.S. = 0.5 V/dec, and $I_{off}$ = 1 pA/um@ $V_d$ = -10V. It is found that the TFTs are very stable after bias stresses such as negative and positive gate biases, hot carrier bias and high current bias. These results indicate that the poly-Si in SLC region is suitable for system on glass (SOG) application.

• 제어로봇시스템학회:학술대회논문집
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• 2002.10a
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• pp.56.3-56
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• 2002

For the weld quality improvement and the convenient operation of machines, laser vision system can be used to track weld seams on pressure vessels. There are many bad conditions to the weld grooves such as cutting error, gap variation of weld joint, and offset error of center line caused by misalignment. We developed a laser vision seam tracking system which consists of a laser vision sensor, a two axis positioning mechanism and a user interface program running on the Windows system. It was found that our system worked well for U, V and X shaped grooves. We used an industrial PC as the system controller to secure immunity to electrical noise and dust. We introduce here a simple and...

• Proceedings of the Optical Society of Korea Conference
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• 2003.07a
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• pp.62-62
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• 2003

Charged particles can be accelerated to relativistic high energies by high power (＞ terawatt) laser beams. We have a research project on laser and plasma-based advanced accelerators in Center for Advanced Accelerators at Korea Electrotechnology Research Institute (KERI), in which the 2 TW (1.4 J／700 fs) Ti：sapphire／Nd：glass hybrid laser system and a He plasma will be used for particle acceleration experiments. In this presentation, we introduce the ongoing research activities and the planned experiments at KERI.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.1
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• pp.29-34
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• 2004

We present the first demonstration of waveguide-type depleted optical thyristor laser diode with InGaAs/InGaAsP multiple quantum well structure. The measured switching voltage and current are 4.63 V and 10uA respectively. The holding voltage and current are respectively 0.59 V, 20uA. The lasing threshold current at the temperature of $25^{\circ}C$ and $10^{\circ}C$ are 111 mAA and 72.5 mA, respectively. The lasing wavelength is centered at 1.561um at a bias current equal to 1.41 times threshold.

• Proceedings of the KIEE Conference
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• 1999.07e
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• pp.2204-2206
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• 1999

Pulsed Nd:YAC laser is used widely for materials processing and instrumentation. It is very important to control the laser energy density in materials processing by a pulsed Nd:YAG laser. A pulse repetition rate and a pulse width are regarded as the most dominant factors to control the energy density of laser beam. In this study, the alternating charge-discharge system was designed to adjust a pulse repetition rate. This system is controlled by one chip microprocessor and allows to replace an expensive condenser for high frequency to a cheap condenser for low frequency. In addition. we have investigated the current pulse shape of flashlamp and the operating characteristics of a pulsed Nd:YAG laser. As a result, it is found that the laser output of the power supply using the alternating charge-discharge system is not less than that of typical power supply. As the pulse repetition rate rises from 30pps to 120pps by the step of 30pps at 1200V, it is found that the laser efficiency decreases but the laser output power increases about 6W at each step.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.2
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• pp.60-68
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• 1997

Rayleigh Scattering Cross Sections($\sigma$i) of various gases and the temperature distributions of premixes C3H8/O2 flame are measured by high power KrF(248nm) Exci- mer laser and ICCD camera. Results show that $\sigma$i of O2 and Propane(C3H8) gases agree well in the 5% error range, but of H2 has the more or less difference from the calcul- ated value by other groups. This is attributed to the low RS signal of H2 to Nosie level(S/N ratio). The temperature distributions of flame range out between 300K in the air and about 2000K in the burned area. In this temperature range, out system has the about 250K temperature resolution. Because low RS signals in the reaction area with high temperature are affected highly by noises, temperature uncertainty of this area is relatively high to another part of flame. Experimental results show that UV Rayleigh Scattering can be used for the measurement of mixing ratio of mixed gases and the temperature distributions of flame. Especially, this technique can be applied for the measurement of the mixing ratio of air/fuel before the ignition and the flame structure after the ignition inside the Engine.

• Proceedings of the KIEE Conference
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• 1989.07a
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• pp.662-666
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• 1989

Pure mono Silane(Purity: 99.99%) was used as a thin film source and [$SiH_4$ + $H_2$ (5%)] + [$PH_3$ + $H_2$(0.05%)] mixed dilute gas was used for p-n junction diode. The substrate was P-type silicon wafer (p=$3{\Omega}$ cm) with the direction (100). The crystalline qualities of deposited thin film were investigated by the X-ray diffraction, RHEED and TED patterns and the voltampere characteristics of p-n junction diode was identified by I-V curve.

• Journal of the Microelectronics and Packaging Society
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• v.12 no.1 s.34
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• pp.73-76
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• 2005

To widen the band gap of ZnO, we have investigated $Zn_{1-x}Mg_xO(ZMO)$ thin films prepared by pulsed laser deposition on c-plane sapphire substrates at $500^{\circ}C$. From X-ray diffraction patterns, ZMO films show only the (0002) and (0004) diffraction peaks. It means that the flints have the wurtzite structure. Segregation of ZnO and MgO phases is found in the films with x=0.59. All the samples are highly transparent in the visible region and have a sharp absorption edge in the UV region. The shift of absorption edge to higher energy is observed in the films with higher Mg composition. The excitonic nature of the films is clearly appeared in the spectra for all alloy compositions. The optical band-gap ($E_g$) of ZMO films is obtained from the ${\alpha}^2$ vs Photon energy plot assuming ${\alpha}^2\;\propto$ (hv - $E_g$), where u is the absorption coefficient and hv is the photon energy. The value of $E_g$ increases up to 3.72 eV for the films with x=0.35. It is important to adjust Mg composition control for controlling the band-gap of ZMO films.