• Current Optics and Photonics
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• 제2권4호
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• pp.303-307
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• 2018

We propose a simple ultraviolet (UV) sensor consisting of a conventional single-mode optical fiber capped with an azobenzene-moiety-containing polymer. The UV light changes the dimensions of the azobenzene polymer, as well as the refractive index of the material. Incident light with a wavelength of 1550 nm was reflected at the fiber/polymer and polymer/air interfaces, and interference of the reflected beams resulted in spectral interference that shifted the wavelength by 0.78 nm at a UV input power of $2.5mW/cm^2$. The UV sensor's response to wavelength is nonlinear and stable. The response speed of the sensor is limited by detection noise, which can be improved by modifying the insertion loss of the UV sensor and the signal-to-noise ratio of the detection system. The proposed compact UV sensor is easy to fabricate, is not susceptible to electromagnetic interference, and only reacts to UV light.

• Journal of electromagnetic engineering and science
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• 제12권1호
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• pp.85-93
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• 2012

We propose a new expression of the near-field gain correction to calculate the on-axis far-field gain from the onaxis near-field gain for a directive antenna. The new expression is represented by transversal vectorial transmitting characteristics of two antennas that are measured by planar near-field equipment. Due to the advantages of the photonic sensor, the utilization of the new expression realizes the measurements of the on-axis far-field gains for two kinds of double ridged waveguide horn antennas within 0.1 dB deviation from 1 GHz to 6 GHz without calibrating the photonic sensor system.

• Current Optics and Photonics
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• 제5권4호
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• pp.444-449
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• 2021

A photonic crystal coupled-cavity waveguide created on silicon-on-insulator is designed to act as a refractive-index-sensing device at midinfrared wavelengths around 4 ㎛. To realize high sensitivity, effort is made to engineer the structural parameters to obtain strong modal confinement, which can enhance the interaction between the resonance modes and the analyzed sample. By adjusting some parameters, including the shape of the cavity, the width of the coupling cavity, and the size of the surrounding dielectric columns, a high-sensitivity refractive-index sensor based on the optimized photonic crystal coupled-cavity waveguide is proposed, and a sensitivity of approximately 2620 nm/RIU obtained. When an analyte is measured in the range of 1.0-1.4, the sensor can always maintain a high sensitivity of greater than 2400 nm/RIU. This work demonstrates the viability of high-sensitivity photonic crystal waveguide devices in the midinfrared band.

• 한국광학회지
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• 제21권5호
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• pp.200-205
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• 2010

본 논문에서는 포토닉 밴드갭 광섬유(Photonic Bandgap Fiber: PBGF) 사이에 중공광섬유(Hollow Optical Fiber: HOF)를 융착 접속시켜 만든 광섬유 간섭계와 넓은 모드 면적을 가지는 광자결정 광섬유(Large Mode Area-Photonic Crystal Fiber: LMA-PCF)사이에 HOF를 융착접속시켜 만든 광섬유 간섭계의 온도 및 스트레인에 대한 광학적 특성을 분석하였다. PBGF 또는 LMA-PCF와 HOF의 융착접속시 광섬유내 공기구멍을 최대한 유지하도록 융착조건을 최적화하여 접속 손실을 줄였다. PBGF와 HOF로 구성된 광섬유 간섭계의 온도 및 스트레인에 대한 민감도는 각각 15.4 pm/$^{\circ}C$와 0.24 pm/${\mu}\varepsilon$으로 측정되었으며, LMA-PCF와 HOF로 구성된 광섬유 간섭계의 온도 및 스트레인에 대한 민감도는 각각 17.4 pm/$^{\circ}C$와 0.2 pm/${\mu}\varepsilon$으로 측정되었다.

• Current Optics and Photonics
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• 제3권3호
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• pp.199-203
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• 2019

The characteristics of a photonic crystal fiber sensor with reuleaux triangle are studied by using the finite element method. The wavelength sensitivity of the designed optical fiber sensor is related to the arc radius of the reuleaux triangle. Whether the core area is solid or liquid as well as the refractive index of the liquid core contributes to wavelength sensitivity. The simulation results show that larger arc radius leads to higher sensitivity. The sensitivity can be improved by introducing a liquid core, and higher wavelength sensitivity can be achieved with a lower refractive index liquid core. In addition, the specific channel plated with gold film is polished and then analyte is deposited on the film surface, in which case the position of the resonance peak is the same as that of the complete photonic crystal fiber with three analyte channels being filled with analyte. This means that filling process becomes convenient with equivalent performance of designed sensor. The maximum wavelength sensitivity of the sensor is 10200 nm/RIU and the resolution is $9.8{\times}10^{-6}RIU$.

• 조명전기설비학회논문지
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• 제29권5호
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• pp.13-18
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• 2015

In this paper, we implemented a polarimetric vibration sensor using a Sagnac birefringence interferometer composed of polarization-maintaining photonic crystal fiber(PM-PCF). By changing the amplitude and frequency of vibration applied to PM-PCF employed as the sensor head of the proposed sensor, sensor responses to various types of vibration were investigated. First, the vibration characteristic of the sensor was explored for a single frequency in a frequency range from 1 to 3000Hz with a cylindrical piezoelectric transducer, and then the sensor response to naturally damped vibration was examined by utilizing a metal cantilever. It was experimentally observed that the sensor output signal was deteriorated by more than 3dB at ~1900Hz in the single frequency vibration measurement with a minimum detectable strain perturbation of ${\sim}1.34n{\varepsilon}/Hz^{1/2}$ at 1500Hz and the peak value of the sensor output signal was proportional to the strength of initially applied stress in the naturally damped vibration measurement.

• Smart Structures and Systems
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• 제5권4호
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• pp.483-494
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• 2009

Damage detection has been proven to be a challenging task in structural health monitoring (SHM) due to the fact that damage cannot be measured. The difficulty associated with damage detection is related to electing a feature that is sensitive to damage occurrence and evolution. This difficulty increases as the damage size decreases limiting the ability to detect damage occurrence at the micron and submicron length scale. Damage detection at this length scale is of interest for sensitive structures such as aircrafts and nuclear facilities. In this paper a new photonic sensor based on photonic crystal (PhC) technology that can be synthesized at the nanoscale is introduced. PhCs are synthetic materials that are capable of controlling light propagation by creating a photonic bandgap where light is forbidden to propagate. The interesting feature of PhC is that its photonic signature is strongly tied to its microstructure periodicity. This study demonstrates that when a PhC sensor adhered to polymer substrate experiences micron or submicron damage, it will experience changes in its microstructural periodicity thereby creating a photonic signature that can be related to damage severity. This concept is validated here using a three-dimensional integrated numerical simulation.

• 한국광학회:학술대회논문집
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• 한국광학회 2007년도 동계학술발표회 논문집
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• pp.217-218
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• 2007

• 조명전기설비학회논문지
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• 제27권2호
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• pp.1-6
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• 2013

In this paper, we implemented a polarimetric strain sensor using a Sagnac birefringence interferometer composed of a polarization-maintaining photonic crystal fiber (PM-PCF). By changing the length of the PM-PCF employed as the sensor head of the proposed sensor, the length dependence of the strain sensitivity was investigated. With respect to 5.0-, 7.5-, and 10.0-cm-long PM-PCFs, strain measurements were done in a measurement range of $0{\sim}6m{\varepsilon}$, and strain sensitivities of ~2.04, ~1.92, and ${\sim}1.73pm/{\mu}{\varepsilon}$ were obtained, respectively. If an ideal PM-PCF with no length dependence of a modal birefringence is used for the proposed sensor, the strain sensitivity is independent of the length of the sensor head (PM-PCF). In the practical PM-PCF used in experiments, however, a shorter PM-PCF has a higher length dependence of the modal birefringence due to its imperfectness and nonuniformity of the internal structure, resulting in a higher length dependence of the strain sensitivity.

• 한국광학회지
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• 제29권6호
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• pp.268-274
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• 2018

본 연구에서는 1차원 포토닉 크리스탈과 금속-유기 구조체 (MOF) 물질인 Hong Kong University of Science and Technology(HKUST-1)을 이용한 수분 감지 컬러 센서를 제안한다. 1차원 포토닉 크리스탈은 주기적인 굴절률 변화에 의해 포토닉 밴드갭이 존재하고, 특정한 파장 대역의 광 성분을 차단 및 반사한다. HKUST-1의 굴절률은 건조한 환경과 습한 환경에서 그 값이 서로 다르다. 여기서 우리는 포토닉 밴드갭의 유무를 활용하여 FDTD 시뮬레이션으로 센서를 설계하였다. 광학 해석 결과, 투과된 광의 색 변환보다 반사된 광의 색 변환이 우수하여 반사된 광을 이용하였다. 그리고 포토닉 밴드갭의 중심 파장이 550 nm인 경우, 건조한 환경 대비 습한 환경의 최대 피크 값이 약 9.5배로 증가했으며, 무채색에서 녹색으로 색 변환이 가능하여 센서로의 특성이 우수하였다. 본 연구 결과는 MOF 물질의 수분 감지 컬러 센서로의 활용을 제시하였으며, MOF 물질의 나노 구조 설계로 산업 디바이스로의 활용성도 확대할 것이다.