• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.1015-1016
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• 2006

The important parameters deciding the fluctuation of Accumulation style surgical operation of ventriculus laser beam are smoothing capacitor, frequency and he characteristics of laser resonator. In this thesis, we control the fluctuation of medical $CO_2C$ laser in realtime by changing Duty-Ratio of IGBT and switching frequency with fixed the smoothing capacitor to improve the fluctuation of laser beam. We detect the light on laser resonator using a CdS photo sensor to improve ripple factor of laser beam and feedback fluctuated signals refined by a band pass filter into the control circuit to stabilize fluctuation actively. There is much to be desired in the realtime controlling technique of the light on Accumulation style surgical operation of ventriculus laser discharge tube in electrical signal. We propose switching control technique with microprocessor and photo sensing technique by controlling switch devices optimum operation and feedback signals detected by a photo sensor into the laser power supply in order to improve ripple factor of the $CO_2$ laser beam.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.714-719
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• 2004

Controlling the cure depth of the Fa1260T photopolymer enhances the quality of a microstructure and minimizes its size in microstereolithography. In this work, variation of cure depth of the Fa1260T photopolymer is investigated while the concentration of a photopolymerization inhibitor as a radical quencher was varied. The energy source inducing photopolymerization was a He-Cd laser and a motorized stage controled the laser beam path accurately. The effects of process variables such as laser beam power and scan speed on the cure depth were examined. Optimum conditions for the minimum cure depth were determined as laser power of 230 W and scan speed of 40-50 m/s at the concentration of the radical quencher of 5％. The minimum cure depth at the optimal condition was 14 m. The feasibility of the fabrication of microstructures such as a microcup, microfunnel, and microgrid of 100 m size is demonstrated using Super IH process.

• Journal of the Semiconductor & Display Technology
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• v.10 no.4
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• pp.131-138
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• 2011

We fabricated distributed feedback InGaAsP/InP laser diodes for optical fiber communication module and characterized the lasing properties in continuous wave operation. The active layer of 7-period InGaAsP(1.127 eV)/InGaAsP(0.954 eV) multi-quantum well structure was grown by the metal-organic chemical vapor deposition. The grating for waveguide was also fabricated by the implementation of the Mach-Zehender holographic method of two laser beams interference of He- Cd laser and the fabricated laser diode has the dimension of the laser length of $400{\mu}m$ and the ridge width of $1.2{\mu}m$. The laser diode shows the threshold current of 3.59 mA, the threshold voltage of 1.059 V. For the room-temperature operation with the current of 13.54 mA and the voltage of 1.12 V, the peak wavelength is about 1309.70 nm and optical power is 13.254 mW.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.1
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• pp.46-50
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• 2004

The curing characteristics of a liquid photopolymer during microstereolithography and the shape accuracy of thereby fabricated microstructures were investigated experimentally. A He-Cd laser with a wavelength of 442nm and a photopolymer consisted of a commercial resin from SK chemical and a photoinitiat or were used for the experiment. By varying the laser beam power and scanning speed of the focused laser beam, minimum curing thickness of 50 ${\mu}ㅡ$ was obtained. The distortion of solidified structure due to adhesion force was measured and the optimum fabrication conditions were determined. Also, the feasibility of direct fabrication of three-dimensional microstructures by Super IH process was examined.

• Journal of the Mineralogical Society of Korea
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• v.22 no.2
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• pp.81-86
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• 2009

The luminescence and fluorescence were investigated by photoluminescence spectroscopy for six gemstones which exhibit color change effect. The shape of luminescence peaks appears different when observed by a photoluminescence spectroscopewith a 514 nm Ar laser source. However, it was not possible to observe the difference in the spectra between the natural and synthetic origins for the same type of gemstones. It was found that the photoluminescence spectrum was related to the crystal structure of the stones. Photoluminescence spectra using a 325 nm He-Cd source reveal that fluorescence is relatively strong for synthetic alexandrite, synthetic color change sapphire and natural alexandrite comparing to the rest of gemstones examined.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.8
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• pp.726-730
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• 2007

Two dimensional photonic crystals (2D PCs) have been fabricated by a double exposure holographic method using a He-Cd laser with a wavelength of 442nm. The arrays of the 2D PCs exhibit variable lattice structures from square to triangle according to a change of rotating angle $({\gamma})$ for double exposure beams. In addition, the period and filling factor of PCs as well as the forms (dot or antidot) could be controlled by experimental conditions. $A l.18-{\mu}m-thick$ resist was spin-coated on Si substrate and the 1st holographic exposure was carried out at incident angle $({\theta})$ of $11^{\circ}$. Then the sample was rotated to ${\gamma}=45^{\circ}{\sim}90^{\circ}$ and the 2nd holographic process was performed at ${\theta}=11^{\circ}$. The variation of diffraction efficiency during the exposure process was observed using a He-Ne laser in real time. The images of 2D PCs prepared were analyzed by SEM and AFM. We believe that the double holographic method is a tool suitable to realize the 2D PCs with a periodic array of large area.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.8-8
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• 2008

Two-dimensional photonic quasicrystal (PQCs) template patterns have been fabricated on a $1.1{\mu}m$-thick DMI-150 photoresist using a multiple-exposure holographic method. A 442-nm HeCd laser was utilized as a light source and the holographic exposure was carried out at a fixed angle of $\theta=6^{\circ}$. After the first holographic exposure, the sample was rotated to a proper angle and the second exposure was performed to the same manner. This exposure process was repeated n/2 times to obtain n-fold symmetric PQC patterns and then the sample was developed. The fabricated PQCs exhibited 8, 10 and 12-fold rotational symmetry and the diffraction patterns using a 632.8-nm HeNe laser were observed for n-rotation symmetry corresponding n-fold PQCs. The fabricated PQC template patterns were examined using scanning electron microscopy(SEM). Transmission spectra were measured fourier transform infrared(FTIR) spectrometer.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.9
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• pp.829-834
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• 2008

Two-dimensional photonic quasicrystal (PQCs) template patterns have been fabricated on a 1.1 ${\mu}m$-thick DMI-150 photoresist using a multiple-exposure holographic method. A 442-nm HeCd laser was utilized as a light source and the holographic exposure was carried out at a fixed angle of ${\theta}$ = 6$^{\circ}$. After the first holographic exposure, the sample was rotated to a proper angle and the second exposure was performed to the same manner. This exposure process was repeated n/2 times to obtain n-fold symmetric PQC patterns and then the sample was developed. The diffraction patterns of the fabricated PQC template were observed using a 632.8-nm HeNe laser. The fabricated PQCs exhibited 8, 10 and 12-fold rotational symmetry, which was in a good agreement with the interference simulation results. In addition, the diffraction patterns with n-rotation symmetry were observed for the corresponding n-fold PQCs. We believe that the multiple-exposure holography is a good method to fabricate the mesoscale PQCs with a high rotational symmetry.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.7-8
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• 2005

Silicon(Si) nanowires have been grown by thermal chemical vapor deposition using the 20h ball-milled SiO powders under controlled conditions without the catalyst. For the synthesis of Si nanowires, $Al_2O_3$ substrates were used. Current-Voltage(I-V) and photoresponses were measured for the single Si nanowire in vacuum at room temperature. The light sources for these measurements were the 325 nm wavelength line from a He-Cd laser and the 633 nm wavelength line from a He-Ne laser. The intensity of the photoresponse is independent of the illumination time. And rise and decay times of the photoresponses are shorter than 1 sec.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.12 s.189
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• pp.128-134
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• 2006

Two-dimensional nano-patterns are fabricated using immersion holographic lithography. The photoresist layer is exposed to an interference pattern generated by two incident laser beams($\lambda$=441.6 nm, He-Cd laser) of which the pitch size is less than 200 nm. Good surface profiles of the 2 dimensional patterns are achieved by trimming the lithography process parameters, such as, exposure time, developing time and refractive index of medium liquid.