• Journal of Welding and Joining
• /
• 제28권5호
• /
• pp.80-85
• /
• 2010

This study focused on laser assisted machining (LAM) of silicon nitride ceramic that efficiently removes the material through machining of the softened zone by local heating. The effects of laser-assisted machining parameters were studied for cost reduction, and active application in processing of silicon nitride ceramics in this study. Laser assisted machining of silicon nitride allows effective cutting using CBN tool by local heating of the cutting part to the softening temperature of YSiAlON using by the laser beam. When silicon nitride is sufficiently preheated, the surface is oxidized and decomposed and then forms bloating, micro crack and silicate layer, thereby making the cutting process more advantageous. HIPSN and SSN specimens were used to study the machining characteristics. Higher laser power makes severer oxidation and decomposition of both materials. Therefore, HIPSN and SSN specimens were machined more effectively at higher power.

• 한국광학회지
• /
• 제4권4호
• /
• pp.428-433
• /
• 1993

공간적으로 Gaussian인 Q-switched Nd:LYAG레이저의 제2고조파 빛살을 일정한 반경의 pinhole로 중심부분만 통과시켜 집광렌즈로 집광시킨 후, 렌즈의 초점면에서 빛살모양을 관찰하여 본 결과 원형 대칭을 갖는 비Gaussian모양을 하고 있음을 확인할 수 있었다. 이 빛살의 집광영역내에서 두께 1mm의 $CS_2$를 이동(z-scan)하여 가며 자체집광효과에 의하여 변화되는 투과도특성을 조사하였다. 측정된 결과를 Fresnel 이론과 1.5% 이내의 오차 범위로 일치함을 알 수 있었고, 자체집광효율이 입사빛의 공간적 모양과 관계함을 확인할 수 있었다.

• Archives of Reconstructive Microsurgery
• /
• 제2권1호
• /
• pp.62-69
• /
• 1993

Recently, conservative and bloodless operative procedures have been focused, so that endoscopic laser have been used. However application of endoscopic laser surgery for laryngeal lesion is capable for followings: (1)capability of delivery through an operating microscope, (2) vaporization of ultraspot. $CO_2$ laser which has been used, has limitations for voice improvement because of 700 micron beam spot. KTP-532 laser which is capable of delivery through an operating microscope vapore 200 micron ultraspot has developed and applied to microlaryngeal surgery. We have experienced 60 cases who were contracted with hoarseness(53 cases of benign lesions vocal nodule 13, vocal polyp 13, bilateral diffuse polyposis of vocal cords 11, intracordal cyst 8, vocal papilloma 5, laryngocele 1, laryngeal stenosis 2 and 7 cases of malignant lesions : laryngeal carcinoma stage I and II) since 1991. We operated them with KTP-532 Laserscope(3 Watt/0.05 sec., pulsed or continuous. San Jose, Calif, USA). Forty eigh cases(90.6%) of 53 bengin laryngeal lesions and 4 cases(57.1%) of malignant lesions were significantly improved in their voices. There were a few complications and technical problems, but laser surgery alone had a limitation to eradicate the disease.

• 한국정밀공학회지
• /
• 제23권9호
• /
• pp.164-173
• /
• 2006

The cooling capacity of a micro-heat pipe is mainly governed by the magnitude of capillary pressure induced in the wick structure. For microchannel wicks, a higher capillary pressure is achievable for narrower and deeper channels. In this study, a metallic micro-heat pipe adopting high-aspect-ratio microchannel wicks is fabricated. Micromachining of high-aspect-ratio microchannels is done using the laser-induced wet etching technique in which a focused laser beam irradiates the workpiece placed in a liquid etchant along a desired channel pattern. Because of the direct writing characteristic of the laser-induced wet etching method, no mask is necessary and the fabrication procedure is relatively simple. Deep microchannels of an aspect ratio close to 10 can be readily fabricated with little heat damage of the workpiece. The laser-induced wet etching process for the fabrication of high-aspect-ratio microchannels in 0.5mm thick stainless steel foil is presented in detail. The shape and size variations of microchannels with respect to the process variables, such as laser power, scanning speed, number of scans, and etchant concentration are closely examined. Also, the fabrication of a flat micro-heat pipe based on the high-aspect-ratio microchannels is demonstrated.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1998년도 하계학술대회 논문집 D
• /
• pp.1444-1446
• /
• 1998

Direct writing of copper lines has been achieved by pyrolytic decomposition of copper formate films using a focused argon ion laser beam($\lambda$ =514.5nm) on a glass. The thickness and linewidth of the deposited copper films were considered as a function of laser power and scan speed. As the result from AES, there are no other elements except for copper after decomposition in the atmospheric ambient.

• 한국진공학회지
• /
• 제5권1호
• /
• pp.1-5
• /
• 1996

Noncrystalline films of diamond-like carbon (DLC) have been prepared by laser ablation technique at room temperature. A Q-switched Nd-YAG laser beam with wavelength of 1064 nm and pulse duration of 10 ns was focused onto a graphite target with power densities of about $10^9 W/\textrm{cm}^2$. The physical properties of the resulting films were analyzed with density, hardness, and resistivity measurements. The surface and bonding structure were investigated by atomic force microscopy (AFM), Raman spectroscopy, electron energy loss spectroscopy (EELS).

• Progress in Superconductivity
• /
• 제12권1호
• /
• pp.17-22
• /
• 2010

Distribution of local critical temperature and current density in $YBa_2Cu_3O_{7-\delta}$ (YBCO) coated conductors was analyzed using a Low-temperature Scanning Laser Microscopy (LTSLM). We prepared YBCO coated conductors of various bridge types to study the spatial distribution of critical temperature and current density in single and multi bridges. An LTSLM system was modified for a detailed two-dimensional scan without shifting of the sample. We observed a spatial distribution of the critical temperature from the bolometric response, which arises from a focused laser beam at the sample near the superconducting transition. Also we studied the relation between the critical temperature and the current density.

• 한국레이저가공학회지
• /
• 제9권1호
• /
• pp.1-7
• /
• 2006

In order to increase the productivity of conventional microstereolithography (MSL), digital micromirror device($DMD^{TM}$) based MSL is proposed and the feasibility of 3D rnicrocomponents fabrication is demonstrated in two ways; free surface and constrained surface techniques. The clearness of optical images at the exposure plane was confirmed for the fabrication of an accurate 3D structure by controlling the dynamic viscosity of FA1260T and the shape accuracy of a structure fabricated with epoxy-based resin ($Somos^{\circledR}$ 10120) was analyzed to determine the optimum curing conditions. After finding the appropriate process variables, the feasibility of multiple microstructures is then demonstrated. Due to the high productivity, MSL using $DMD^{TM}$ showed the potential to replace the existing focused laser beam MSL.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1997년도 하계학술대회 논문집 E
• /
• pp.1807-1809
• /
• 1997

The salt contamination on the surface of the porcelain insulators used electric power systems causes flash-over accidents. Therefore the quantity of salt contamination should be monitored not to exceed a limit. In this study, we tried laser aided measurement of salt contamination. The Nd:YAG laser beam was focused on the surface of the porcelain insulators which were artificially contaminated, and we detected the D-Line (${\cong}589nm$) of spontaneous emission from the excited sodium atoms with a PMT and an oscilloscope. And we deduced the relation between the detected signals and degree of salt contamination.

• International Journal of Precision Engineering and Manufacturing
• /
• 제8권2호
• /
• pp.54-58
• /
• 2007

This paper describes an atomic force microscope (AFM)-based instrument for measuring the nanoscale cutting edge profiles of diamond cutting tools. The instrument consists of a combined AFM unit and an optical sensor to align the AFM tip with the top of the diamond cutting tool edge over a submicron range. In the optical sensor, a aser beam is emitted from a laser diode along the Y-axis and focused to a small beam spot with a diameter of approximately $10{\mu}m$ at the beam waist, which is then received by a photodiode. The top of the tool edge is first brought into the center of the beam waist by adjusting it in the X-Z-plane while monitoring the variation in the photodiode output. The cutting tool is then withdrawn and its top edge position at the beam center is recorded. The AFM tip can also be positioned at the beam center in a similar manner to align it with the top of the cutting edge. To reduce electronic noise interference on the photodiode output and thereby enhance the alignment accuracy, a technique is applied that can modulate the photodiode output to an AC signal by driving the laser diode with a sinusoidal current. Alignment experiments and edge profile measurements of a diamond cutting tool were carried out to verify the performance of the proposed system.