• Current Optics and Photonics
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• 제3권5호
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• pp.401-407
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• 2019

Polymeric optical waveguide devices with Bragg gratings have been investigated, for implementing tunable lasers and wavelength filters used in wavelength-division-multiplexed optical communication systems. Owing to the excellent thermo-optic effect of these polymers, wavelength tuning is possible over a wide range, which is difficult to achieve using other optical materials. In this study the phase-mask technology, which has advantages over the conventional interferometeric method, was introduced to facilitate the fabrication of Bragg gratings in polymeric optical waveguide devices. An optical setup capable of fabricating multiple Bragg gratings simultaneously on a 4-inch silicon wafer was constructed, using a 442-nm laser and phase mask. During fabrication, some of the diffracted light in the phase mask was totally reflected inside the mask, which affected the quality of the Bragg grating adversely, so experiments were conducted to solve this issue. To verify grating uniformity, two types of wavelength-filtering devices were fabricated using the phase-mask lithography, and their reflection and transmission spectra were measured. From the results, we confirmed that the phase-mask method provides good uniformity, and may be applied for mass production of polymer Bragg-grating waveguide devices.

• 한국버섯학회지
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• 제18권1호
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• pp.10-19
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• 2020

Light is an important factor for cordycepin production in Cordyceps militaris. We investigated the effects of different light-emitting diode (LED) conditions including various LED wavelengths and their combinations on cordycepin production in Cordyceps militaris cultivated in submerged culture. The results of our study showed that the combinations of LED wavelengths were more beneficial than single LED sources for cordycepin production. Among the three tested wavelength combinations, the greatest effects for cordycepin production were observed for the red:blue light combination at the wavelength ratio of 5:5 or 3:7. The optimal culture conditions were 19.2278 h/day of illumination time; 9.19497 g/50 mL of glucose content in the media; and 53.112 h of cultivation time. Our model predicted a maximum yield of 2860.01 ㎍/mL cordycepin. Finally, to verify the calculated maximum, we performed experiments in the culture media representing the obtained optimum combination and the cordycepin yield of 2412.5 ㎍/mL.

• 반도체디스플레이기술학회지
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• 제21권3호
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• pp.39-44
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• 2022

The light extraction technology for improving the light efficiency of OLEDs is the core technology for extracting the light inside the OLEDs to the outside. This study demonstrates a simple method to generate random nanostructures (RNSs) containing high refractive index nanoparticles to improve light extraction and viewing angle characteristics. A simple dry low-temperature process makes the nanostructured scattering layer on the polymer resin widely used in the industry. The scattering layer has the shape of randomly distributed nanorods. To control optical properties, we focused on changing the shape and density of RNSs and adjusting the concentration of high refractive index nanoparticles. As a result, the film of the present invention exhibits a perpendicular transmittance of 85% at a wavelength of 550 nm. This film was used as a scattering layer to reduce substrate mode loss and improve EL efficiency in OLEDs.

• 의료ㆍ복지 건축 : 한국의료복지건축학회 논문집
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• 제29권3호
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• pp.29-36
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• 2023

Purpose: The purpose of this study is to find out whether the color change of the LED light source has a significant effect on the beta wave activity of EEG in the learning state. Methods: The subjects of the experiment were 20 male and female college students between the ages of 19 and 25 who routinely perform their studies. In the created learning environment, the EEG change according to the change in the lighting color was measured while solving the Mensa thinking ability problem while sitting on a desk with LED lights installed on the top and a chair with a footrest to stabilize the legs. The light source consisted of 3 ready-made colors and 6 newly created colors. A total of 9 color light stimuli were given for 2 minutes each, and the EEG change of the subject was observed. After the experiment, the correlation was analyzed based on the mid-beta wave data recorded on the QEEG according to the color change of light and the Mensa problem score. Results: It was found that the activation of mid-beta waves was stimulated in the temporal lobes (T5, T3, T6, T4) and occipital lobes (O1, O2) of all subjects who focused on solving Mensa thinking problems. As a result of comparing the top 20% and the bottom 20% of problem solving scores, the upper group had no effect of lighting, while the lower group showed increased beta wave activity in response to color light stimulation in the order of T4, T6, and T5. Implications: It was confirmed that the color of light that activates the middle beta wave varies greatly depending on the subject's attention and learning ability, and it is judged that the color of light including the green wavelength is helpful in activating the middle beta wave in the group with low learning ability.

• Medical Lasers
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• 제8권2호
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• pp.50-58
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• 2019

Background and Objectives Low-level light therapy (LLLT) is an application of low-power light for various purposes such as promoting tissue repair, reducing inflammation, causing analgesia, etc. A previous study suggested the effect of light emitting diode (LED) light with the wavelength of 740 nm for promoting wound healing of corneal epithelial cells. This current study aimed to confirm the effect of LLLT for managing inflammation of a dry eye disease (DED) mouse model. Materials and Methods A total of 50C57BL/6 female mice were randomly grouped into 5 groups to compare the effect of LLLT:1) Control group, 2) Only LLLT group, 3) Dry eye group, 4) LLLT in dry eye group, and 5) Early treatment group. DED was induced with 4 daily injections of scopolamine hydrobromide and desiccation stress for 17 days, and LLLT at 740 nm was conducted once every 3 days. To analyze the effect of LLLT on the DED mouse model, tear volume, corneal surface irregularities, and fluorescence in stained cores were measured, and the level of inflammation was assessed with immunohistochemistry. Results The DED mouse model showed significant deterioration in the overall eye condition. After LLLT, the amount of tear volume was increased, and corneal surface irregularities were restored. Also, the number of neutrophils and the level of inflammatory cytokines significantly decreased as well. Conclusion This study showed that LLLT at 740 nm was effective in controlling the corneal conditions and the degree of inflammation in DED. Such findings may suggest therapeutic effects of LLLT at 740 nm on DED.

• 마이크로전자및패키징학회지
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• 제23권4호
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• pp.63-67
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• 2016

Divalent europium-activated $Ca_2PO_4Cl$ phosphor powders were prepared by a chemical synthetic method followed by heat treatment in reduced atmosphere, and the crystal structures, morphologies and photoluminescence properties of the powders were investigated by x-ray powder diffraction, scanning electron microscope and spectrometer. The effect of Ca/P mole ratio at the starting materials on the final products was evaluated. The optimized synthesis condition obtained in this study was Ca/P mole ratio of 2.0. The present phosphor materials had higher photoluminescence intensity and better color purity than the commercial blue phosphor powders, $(Ca,Ba,Sr)_{10}(PO_4)_6Cl_2:Eu^{2+}$. The result of excitation spectrum measurement indicated that the excitation efficiency of the synthesized powders was higher for the long-wavelength UV region than that of the commercial phosphor. It was thus concluded that the samples prepared in this study can be successfully applied for the light-emitting devices such as LED excited with long-wavelength UV light sources.

• 한국식품조리과학회지
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• 제31권4호
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• pp.505-509
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• 2015

본 연구는 식물 공장에서 특정 파장을 조합한 혼합 LED를 광원으로 사용하여 방울토마토와 적채를 재배할 때 식물의 성장과 각각에 존재하는 생리활성물질인 리코펜과 안토시아닌의 함량 변화를 탐색하였다. 대조광으로 형광등을 사용하였고 LED 혼합 파장은 적색, 녹황색, 청색 파장(630 nm:550 nm:450 nm=8:1:1)을 혼합하여 방울토마토와 적채에 조사하였다. 방울토마토에서는 LED을 조사하였을 때, 수확되는 방울토마토의 개수는 적었으나 수확된 방울토마토의 무게와 당도에서 유의적으로 높은 값을 나타내었다. 그러나 방울토마토의 생리활성 물질인 리코펜의 함량은 LED 조사 시 오히려 낮았다. 적채는 LED를 조사하였을 때, 형광등에 비해 적체의 무게에서 유의적으로 높은 값을 나타내었고, 안토시아닌 함량 또한 유의적으로 증가시켰다. 결론적으로 작물의 색에 따라 성장에 요구하는 LED의 파장 및 혼합 비율이 다르다는 것을 알았고, 과실의 색에 따라 LED 파장의 혼합 비율을 달리하는 것이 필요하다는 것을 보여주었다.

• Journal of Information Display
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• 제9권4호
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• pp.21-29
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• 2008

We studied both the wavelength and intensity dependent photo-responses (photofield-effect) in amorphous In-Ga-Zn-O (a-IGZO) thin-film transistors (TFTs). During the a-IGZO TFT illumination with the wavelength range from $460\sim660$ nm (visible range), the off-state drain current $(I_{DS_off})$ only slightly increased while a large increase was observed for the wavelength below 400 nm. The observed results are consistent with the optical gap of $\sim$3.05eV extracted from the absorption measurement. The a-IGZO TFT properties under monochromatic illumination ($\lambda$=420nm) with different intensity was also investigated and $I_{DS_off}$ was found to increase with the light intensity. Throughout the study, the field-effect mobility $(\mu_{eff})$ is almost unchanged. But due to photo-generated charge trapping, a negative threshold voltage $(V_{th})$ shift is observed. The mathematical analysis of the photofield-effect suggests that a highly efficient UV photocurrent conversion process in TFT off-region takes place. Finally, a-IGZO mid-gap density-of-states (DOS) was extracted and is more than an order of magnitude lower than reported value for hydrogenated amorphous silicon (a-Si:H), which can explain a good switching properties observed for a-IGZO TFTs.

• 한국정보전자통신기술학회논문지
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• 제3권2호
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• pp.18-24
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• 2010

본 연구에서는 표준 색차계와의 비교와 색상정보 좌표계 분석법을 이용하여, 비접촉 및 비파괴 측정 장치로 많은 분야에서 사용하고 있는 내장형 분광광도계의 조명 영향을 평가하였다. 본 연구에서 사용한 색상지는 표준 반사물질과 만셀 표준 색상인 빨강, 노랑, 초록, 파랑 색상지를 사용하였다. 표준 색차계 시스템 및 내장형 분광광도계 시스템을 비교 분석하기 위하여, 실험 재료 색상지를 색상지별 20번 측정하였다. 본 연구에서는 비접촉 및 비파괴 검사 장치에 내장형 분광광도계 응용에서 조명을 일정하게 공급하고 캘리브레이션을 정확하게 수행한다면, 조명의 영향을 거의 받지 않는 시스템을 구성할 수가 있을 것으로 판단되었다.

• 생물환경조절학회지
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• 제22권1호
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• pp.49-54
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• 2013

국화생육에 있어서 LED광이 미치는 영향을 구명하기 위해서 국화 'Shinma'를 대상으로 단일광 적색광(Red) 650nm, 647nm, 622nm, 청색광(Blue) 463nm, 450nm, 백색광(White)과 혼합광(적색광(Red) :청색광(Blue)-(9 : 1, 8 : 2, 7 : 3, 6 : 4, 5 : 5), 적색광(Red) :백색광(White)-(7 : 3) 그리고 광원의 조사시간에 따른 LED효과를 구명하고자 광원 비율 적색광(Red) : 청색광(Blue)-(8 : 2)의 컨트롤 베드를 3개로 구성하고, 대조구(태양광)를 포함하여 총 15개의 컨트롤 베드를 구성하여 수행하였다. 광 조사시간에 따른 생육에서는 6/6(on/off)에서 초장, 엽수, 생체 중, 엽면적이 높게 나타났지만, 전체적으로 통계적인 유의성은 인정되지 않았다. 단일광원의 경우 청색광(Blue) 450nm에서 초장과 엽면적이 가장 크게 나타났고, 근장에서는 적색광(Red) 650nm에서 가장 높게 나타났다. 그 외의 측정항목에서는 대조구(태양광)와 백색광(White)에서 높게 나타나, 단일광원에 대한 영향도 있지만, 다양한 파장대의 광원도 작물 생육에 필요한 것으로 판단된다. 혼합광의 경우 단일광과 달리 대조구(태양광)를 제외하고 적색광(Red)의 비율이 가장 높은 적색광(Red) :청색광(Blue)-(9 : 1)에서 초장이 가장 높게 나타났으며, 생체중과 건물중에서는 적색광(Red) : 백색광(White)-(7 : 3)에서 가장 높게 나타났다. 그 다음으로는 대조구(태양광)에서 높게 나타났으며, 엽면적에 있어 대조구(태양광)가 가장 높게 나타났다. 국화생육에 있어서 LED광이 미치는 영향을 구명한 결과 국화의 생장 및 형태형성에 분명히 영향을 미치는 것으로 보였으며, 단일광과 혼합광에 대해 적절한 광원의 선택은 보광의 목적이나 고품질 국화생산을 위해 필요하다고 판단된다.