• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.535-538
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• 2000

We have investigated the photoinduced anisotropy in chalcogenide $As_{40}Ge_{10}Se_{15}S_{35}$ thin films, non-doped and photodoped by Ag and Cu. The films were exposed by the linearly polarized He-Ne laser light( $\lambda$=632.8nm). The Ag and Cu photodoping resulted in reducing the time of saturation photoinduced linearly dichroism. Also photoinduced linearly dichroism was increased up to maximum 184% by Ag photodoping and 138% by Cu photodoping, respectively. As the result of this study, the linearly dichroism can be interesting for different applications of photoinduced anisotropy. In addition, it will offer lots of information for the photodoping mechanism and analysis of chalcogenide thin film.

• Journal of the Korean Vacuum Society
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• v.8 no.4B
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• pp.530-535
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• 1999

W made a near-field optical microscope(NSOM) apparatus and evaluated it. To control the distance between a tip and a sample, we used a piezoelectric translator and a He-Ne laser, and consequently obtained the spatial resolution better than 100nm. For the semiconductor spectroscopic applications, we performed photoluminescence and photocurrent experiments on the GaAs/AlGaAs MQWs samples. In the case of PL experiment, we obtained the low signal to nose ration due to the extremely small power of a light source passing through the nanometric optical fiber tip. However photocurrent experiment shows a hundred times better signal to noise than that of PL experiment. This suggests that photocurrent experiment using NSOM have the possibility to provide the spatial resolution better than 10nm.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.6
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• pp.533-537
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• 2000

It was known that chalcogenide glasses have the superior property of the photoinduced anisotropy(PA). In this study we observed the phenomenon of Ag polarized-photodoping in chalcogenide As$_{40}$ /Ge$_{10}$/Se$_{15}$ /S$_{35}$ and the double-layer of Ag doped As$_{40}$ /Ge$_{10}$/Se$_{15}$ /S$_{35}$ thin film using the irradiation with the polarized He-Ne laser light. The Ag polarized-photodoping results in reducing the time of saturation anisotorpy and increasing the sensitivity of linearly anisotropy intensity up to maximum 220% The Ag polrized-photodoping shows improvement of the photoinduced anisotropy property in polarized photodoping of the chalcogenide thin film. It will offer lots of information for the photodoping mechanism and analysis of chalcogenide thin film.in film.ilm.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.9
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• pp.781-785
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• 2000

Chalcogenide glasses are suggested as a candidate for optical recording. In this study, we have investigated the holography recording and reconstruction of the polarization state in chalcogenide As$_{40}$ Ge$_{10}$Se$_{15}$ S$_{35}$ thin films. We have used a He-Ne laser light(633nm) to probe and record of the grating. Also the polarization state of object beam was modulated with a λ/4 wave plate. The polarization state of the +1st order diffracted beam was generated by readout of the grating with a linearly polarized reference beam. It was the same-handed polarization state as the polarization state of the recording beam. The result is shown that the diffraction efficiency of circularly polarized recording represents higher than other polarization state.ate.e.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.219.2-219.2
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• 2012

We are developing Adaptive Optics (AO) system for 24 inch telescope at Seoul National University Observatory. It consists of the tip-tilt correction system and the residual wavefront error correction system with a deformable mirror and a wavefront sensor. We present the construction and performance measurements of the tip-tilt correction system. The tip-tilt component is the single largest contributor to wavefront error, especially for small telescope. The tip-tilt correction system consists of a quadrant photodiode, a tip-tilt mirror and a feed back loop. The collimated He-Ne laser beam is used for input light source and is artificially disturbed by air turbulence generated by a heat gun. Most of the turbulence is of low frequency less than 20 Hz, but extends to a few hundreds Hz. It is found that the closed loop system using proportional-integral-derivative (PID) control successfully corrects tip-tilt error at a rate as high as 300~400 Hz.

• Corrosion Science and Technology
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• v.2 no.6
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• pp.277-282
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• 2003

Holographic interferometry, an electromagnetic method, was used to study corrosion of carbon steel, aluminum and copper nickel alloys in NaOH, KCI and $H_2SO_4$ solutions respectively. The technique, called electrochemical emission spectroscopy, consisted of in-situ monitoring of changes in the number of fringe evolutions during the corrosion process. It allowed a detailed picture of anodic dissolution rate changes of alloys. The results were compared to common corrosion measurement methods such as linear polarization resistance measurements and electrochemical impedance spectroscopy. A good agreement between both data was found, thus indicating that holographic interferometry can be a very powerful technique for in-situ corrosion monitoring.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.299-302
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• 2000

In this study, we have made the large holographic surface relief gratings on amorphous chalcogenide $As_{40}$$Ge_{10}$$Se_{15}$$S_{35}$ films by two beam interference using a He-Ne laser(632.8nm) light. The film thickness was about 0.6$\mu\textrm{m}$, we could magnify beam size by using beam expander. We made use $90^{\circ}$ holder which was made of reflection mirror and sample. Formed the surface relief structures were investigated using optical microscope. The diffraction efficiency was obtained by measuring +lst order intensity. In addition we investigated grating formation and diffraction efficiency as a function of polarization states which is linear or circular polarization. The results indicate that the grating was formed by linear polarized beam is better clear than that by circular polarized beam.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.574-577
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• 1999

The chalcogenide glasses of thin films have superior property of the photoinduced anisotrophy(PA). In this study, we observed the phenomenon of Ag polarized photodoping using the irradiation with polarized He-Ne laser light, in the thin film of chalcogenide As/sub 40//Ge/sub 10//Se/sub 15//S/sub 35/ and the double-layer of Ag doped As/sub 40//Ge/sub 10//Se/sub 15//S/sub 35/. The Ag polarized photodoping result in reducing time of saturation anisotrophy and increasing sensitivity of linearly anisotrophy intensity, up to maximum 220%. In the thin films of chalcogenide, the Ag polarized photodoping will be show a capability of new method that suggested more improvement of photoinduced anisotrophy property

• Proceedings of the KIEE Conference
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• 2000.11c
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• pp.419-421
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• 2000

In this study, we observed the photoinduced birefringence of Ag polarized-photodoping in chalcogenide thin film and the double-layer of Ag doped chalcogenide thin film using the irradiation with the polarized He-Ne laser light. The photoinduced birefringence of Ag polarized-photodoping results in increasing the sensitivity of linearly anisotropy intensity and birefringence(${\Delta}n$). The Ag polarized-photodoping shows improvement of the photoinduced anisotropy property, in polarized photodoping of the chalcogenide thin film. It will offer lots of information for the photodoping mechanism and analysis of chalcogenide thin film.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.87-90
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• 1999

The dependence of diffraction efficiency as a funct~on of film thickness and incident angle has been investigated in amorphous chalcogenide thin films, which act as a polarization holographic materials. Especially a-(Se, S) based films exhibit a number of photoinduced phenomena not observed in other types of amorphous thin films. Holographic gratings in amorphous As-Ge-Se-S thin films have been formed using the mutual perpendicular polarized(linearly) He-Ne laser light. We could obtain the optimum condition to get high diffraction efficiency.