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D. Jung(정대웅),N. Do(도남곤),J. Lee(이준엽) Korean Society for Precision Engineering 2021 한국정밀공학회 학술발표대회 논문집 Vol.2021 No.11월
A highly sensitive and selective non-dispersive infrared (NDIR) CO₂ gas sensor requires achieving high transmittance and narrow full width at half maximum (FWHM), which depends on the interface of the optical filter for precise measurement of CO₂ concentration. This paper presents the design, simulation, and fabrication of a Fabry-perot filter based on a distributed Bragg reflector (DBR) for a low-cost NDIR CO₂ sensor. The Fabry-perot filter consists of upper and lower DBR pairs, which comprise multilayered stacks of alternating high- and low-index thin films, and a cavity layer for the resonance of incident light. As the number of DBR pairs inside the reflector increases, the FWHM of the transmitted light becomes narrower, but the transmittance of light decreases substantially. Therefore, it is essential to analyze the relationship between the FWHM and transmittance according to the number of DBR pairs. The DBR is made of silicon and silicon dioxide by RF magnetron sputtering on a glass wafer. After the optimal conditions based on simulation results were realized, the DBR exhibited a light transmittance of 38.5% at 4.26 μm and an FWHM of 158 nm. The improved results substantiate the advantages of the low-cost and minimized process compared to expensive commercial filter.
부영양화 사전 예방을 위한 휴대용 총인 모니터링 시스템 개발
정동건 ( Dong Geon Jung ),김승덕 ( Seung Deok Kim ),권순열 ( Soon Yeol Kwon ),이재용 ( Jae Yong Lee ),김유성 ( Yu Seong Kim ),이준엽 ( Junyeop Lee ),김재건 ( Jaekeon Kim ),김세완 ( Sae-wan Kim ),공성호 ( Seong Ho Kong ),정대웅 ( D 한국센서학회 2020 센서학회지 Vol.29 No.5
In this study, a portable total-phosphorus (TP) monitoring system utilizing a photocatalytic-reaction-based pretreatment method is proposed, fabricated, and characterized. Commercial TP monitoring systems are only used in laboratories because of their complex monitoring procedure, bulk-size, and high-cost. In particular, pretreatment in commercial TP monitoring systems is performed at high temperatures (> 120 ℃) and pressure (> 1.1 kg cm<sup>-2</sup>) making it difficult to minimize the scale of the systems. The proposed TP monitoring system employs a pretreatment method with a photocatalytic reaction; thus, its size can be reduced, as photocatalytic reactions occur at room temperature and atmospheric pressure. Analytes with various TP concentrations are pretreated using the proposed portable TP monitoring system and are quantitatively measured with an LED and a photodiode.