• Korean Journal of Optics and Photonics
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• v.9 no.1
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• pp.25-30
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• 1998

In this paper, a simple scheme of optical interconnections between M input and N output terminals using mode speckle patterns generated in the mulitmode optical fiber is described. It is shown that fully parallel nonblocking interconnections are accomplished by using properly generated mode speckle patterns as destination codes and dectecting the generated mode speckle patterns separately using M multiplexed Vander Lugt matched filters at each output terminal. The orthogonality condition of mode speckle patterns is investigated by either changing the launching angles or rotating the polarization direction of the beam. Preliminary experiments by use of a 4$\times$4 graded refractive-index multimode fiber coupler whose core diameter was 50 ${\mu}{\textrm}{m}$ were performed to show the feasibility of our scheme.

• Korean Journal of Optics and Photonics
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• v.3 no.3
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• pp.198-202
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• 1992

Silver ion-exchanged glass waveguide with its large surface index difference and shallow depth is suitable to be used for the hybrid integration of semiconductor device and glass waveguide using the semiconductor film grafting technique. We report characteristics of the planar and channel glass waveguides exchanged in the diluted silver nitrate melt in the visible and infrared spectral region. Especially, we determined the fabrication parameters for single-mode channel waveguide at 1.5.$\mu$m, an important wavelength in the optical communication. Directional couplers with several different configurations were fabricated, and their 3 dB coupling length was determined as a function of wavelenGh and polarization.

• Journal of IKEEE
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• v.23 no.2
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• pp.606-613
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• 2019

In this paper, a new method for flat sweeping automatic hold of wavelength swept laser has proposed. Through the performance test on the implemented laser, even 5 hours passed, the flat sweeping has held up well, and 56nm flat sweeping range, 1kHz sweeping frequency, and 8.8mW average optical power were obtained. This showes that the proposed can eliminate the necessity of hand-operated polarization control required for previous swept lasers in case of long time operation and also optical spectrum analyzer needed to monitor the sweeping spectrum status.

• Korean Journal of Heritage: History & Science
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• v.37
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• pp.349-369
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• 2004

Today, in the cultural properties research, there are several methods for knowing the culture of the past through a lot of information that remains and relics contain. Especially, statistical method like presumption of producing center were introduced from computer development at the early 20th century. This study showed the characteristic about firing historic sites presumed as a tile-kiln in the remains of Cheonwang temple sites, Hanam, Gyeonggi province. Also, I used nature scientific methods for correlation between tiles excavated at historic sites and circumference building and obtained there results as follows. First, soft tile parts showed similar water suction ratio(over 10%) like another tiles, except hard tile parts. Second, identification about mineral crystallization in a sample showing low water suction ratio confirmed a result that Mullite, Tridymite, Cristobalite as high temperature crystal form were presented. I know that firing temperature was higher than the other tile parts from this result. Third, statistical analysis from micro-component resulted that tiles excavated at firing historic sites and Cheonwang temple sites were closely connected. As the results, I knew that the tiles got a supply after the establishment of tile-kiln, not at a long distance at the period of Cheonwang temple construction.

• Journal of Korean Society of Transportation
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• v.33 no.3
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• pp.284-293
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• 2015

The objective of this paper is to determine the conditions of road surface by utilizing the images collected from closed-circuit television (CCTV) cameras installed on roadside. First, a technique was examined to detect wet surfaces at nighttime. From the literature reviews, it was revealed that image processing using polarization is one of the preferred options. However, it is hard to use the polarization characteristics of road surface images at nighttime because of irregular or no light situations. In this study, we proposes a new discriminant for detecting wet and dry road surfaces using CCTV image data at night. To detect the road surface conditions with night vision, we applied the wavelet packet transform for analyzing road surface textures. Additionally, to apply the luminance feature of night CCTV images, we set the intensity histogram based on HSI(Hue Saturation Intensity) color model. With a set of 200 images taken from the field, we constructed a detection criteria hyperplane with SVM (Support Vector Machine). We conducted field tests to verify the detection ability of the wet road surfaces and obtained reliable results. The outcome of this study is also expected to be used for monitoring road surfaces to improve safety.

• Polymer(Korea)
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• v.25 no.1
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• pp.115-121
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• 2001

High molecular weight syndiotactic poly(vinyl alcohol)(HMW s-PVA) with number-average degree of polymerization of 10000 and syndiotactic diad content of 61.5%/iodine complex film was prepared. Its adsorption and desorption behaviors of iodine in hot water were investigated. In comparison with atactic PVA film or low molecular weight s-PVA film, the degree of solubility of s-PVA film and the iodine desorption of HMW s-PVA/iodine film in hot water were limited to an extremely lower level. As the soaking time increased, the iodine desorption in hot water was increased. This reason might be explained by the fact that as the soaking time increased, so the iodine adsorption increased not by the stable molecular complex between PVA and iodine but by the simple physical adsorption of iodine.

• Korean Journal of Optics and Photonics
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• v.20 no.6
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• pp.354-360
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• 2009

We have constructed and analyzed the performance of a simple fiber bundle multi-focal microscope. The microscope had a fiber bundle substituted for micro-lens array that is the core part of MMM(multi-focal multi-photon microscope). The MMM is a type of confocal microscope. To analyze the performance and characteristics of the fiber bundle multi-focal microscope, three types of samples were used: a standard grating, USAF 1951(7, 3), and 1951(7, 6). Using two polarizers and a polarizing beam splitter, we eliminated noise and got clear images. We obtained the FWHM of fiber spot images with the standard grating using two different magnifier lenses which were 63X and 20X, and found an image of the sample as a distribution of fiber spot images. For this case we used the low magnification lens, which gives denser distribution, so that we could get clearer images. In order to test the resolution of the fiber bundle multi-focal microscopic system, we used the USAF 1951 sample which has a smaller line interval than that of the standard grating. The FWHM of the line width of the image coincides well with the real line width of the USAF 1951 sample. We confirmed the performance of a fiber bundle multi-focal microscopic system which is relatively simple but has submicron resolution and is able to get 1600 images at the same time.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.161-161
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• 2010

InAsSb alloy system 은 HgCdTe 를 대체하는 적외선 광소자 및 검출기 등에 응용이 가능한 유망한 물질이지만 정확한 유전함수 및 전이점의 연구는 미흡한 실정이다. 본 연구에서는 타원 편광 분석법을 이용하여 1.5 ~ 6 eV 의 분광 영역에서 As 조성비를 각기 (x = 0, 0.127, 0.337, 0.491, 0.726 및 1.00) 다르게 한 $InAs_xSb_{1-x}$ alloy의 유전함수를 측정하였다. 또한 표면에 자연산화막을 제거하기 위하여 Methanol 과 DI Water 로 표면을 세척 한 후 $NH_4OH$, Br in Methanol, HCl 등으로 적절한 화학적 에칭을 하여 산화막을 제거함으로서 순수한 InAsSb 의 유전함수를 측정할 수 있었다. 측정된 InAsSb 유전함수를 Standard analytic critical point line shape 방법으로 As 조성비에 따른 에너지 전이점을 얻을 수 있었다. 또한 얻어진 에너지 전이점 값을 이용하여 linear augmented Slater-type orbital 방법으로 전자 밴드 구조 계산을 하였고, 이를 바탕으로 $E_0$, $E_1$, $E_2$ 전이점 지역의 여러 전이점 ($E_1$, $E_1+\Delta_1$, $E_0'$, $E_0'+\Delta_0'$, $E_2$, $E_2+\Delta_2$, $E_2'$, $E_2'+\Delta_2$, $E_1'$) 의 특성을 정확히 정의할 수 있었다. 또한 As 조성비가 증가하면서 $E_2$, $E_2+\Delta_2$, $E_2'$, $E_2'+\Delta_2$ 전이점들이 서로 교차 되는 것을 발견하였고, 저온에서만 관측이 가능하였던 InSb 의 두 saddle-point (${\Delta_5}^{cu}-{\Delta_5}^{vu}$, ${\Delta_5}^{cl}-{\Delta_5}^{vu}$)를 상온에서 찾아내었다. 타원 편광 분석법을 이용한 전이점 연구 및 물성 분석은 InAsSb alloy 의 광학적 데이터베이스를 확보하는 성과와 더불어 새로운 디바이스기술 및 광통신 산업에도 유용한 정보가 될 것이다.

• Korean Journal of Optics and Photonics
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• v.17 no.3
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• pp.278-284
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• 2006

We have fabricated and measured electrooptic modulator using coupled stack InAs/InGaAs quantum dots. The height of the quantum dot is 16 nm and quantum dots are stacked including an InGaAs capping layer. The peak wavelength of photoluminescence is 1260 nm at room temperature and 1158 nm at 12 K. The operation characteristics of the quantum dots show high modulation efficiency of electrooptic modulator at 1550 nm compared to that of existing III-V bulk and MQW type semiconductor. The measured switching voltage ($V\pi$) is 540 and 600 mV, for TE mode and TM mode, respectively. From the results, the modulation efficiency can be determined as 333.3 and $300^{\circ}/V{\cdot}mm$ for TE and TM modes. The results reported here may lead to the design and fabrication of a novel electrooptic modulator with low switching voltage and high efficiency.

• Journal of the Korean Chemical Society
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• v.42 no.3
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• pp.315-322
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• 1998

A series of new dimesogenic compounds were prepared and their thermotropic and liquid crystalline properties were studied by differential scanning calorimetry and on a hot-stage of a polarizing microscope. These compounds, 1,10-bis[2,5-bis(4-substitutedphenoxycarbonyl)phenoxy]decanes, consist of two bis(ρ-substitutedphenoxy)terephthalate units interconnected through a oxydecamethyleneoxy spacer on the central terephthaloyl units resulting in the structure of "H-shaped" dimeric twin compounds. The terminal substitutent groups were changed; X=-F, -H, -I, -Cl, -Br, $-NO_2,\;-CF_3,\;-OC_4H_9,\;-CN\;and\;-C_6H_5.$ The compounds with X=$-OC_4H_9,\;-CN\;and\;-C_6H_5$ were monotropically nematic. In contrast, the compounds with $X=-F, -H, -I, -Cl, -Br, $-NO_2\;and\;-CF_3$ were non-liquid crystals. The nematic group efficiency of these compounds was in the order of -C_6H_5>-CN>-OC_4H_9.$