• 전기전자학회논문지
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• 제12권4호
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• pp.234-238
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• 2008

We demonstrate a simple method to generate a stable 40 GHz pulse train at 1550 nm by spectral filtering of a 10 GHz mode.locked pulse source using a fiber Fabry-Perot interferometer (FFPI). A high finesse FFPI with a 40 GHz free spectral range blocks successfully unwanted spectral components of a 10 GHz pulse source and passes only 40 GHz spaced spectral lines ensuring pulse repetition-frequency quadruplication of the input pulses.

• 한국전기전자재료학회논문지
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• 제24권11호
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• pp.915-919
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• 2011

We analyzed various forces affective to the charged particles in closed space, to explain the image degradation and lifetime-shortening phenomena because of particle lumping which is one of the serious problems in reflective displays. It is possible to predict the quantity of q/m which is the most important parameter in determining the optical and electrical characteristics, by calculating the image force and kinetic energy. For stable driving, the quantity of q/m must be in the defined range but it changes during the fabrication process, so we added the filtering process to solve this problem and obtained the well-defined nonlinear driving voltage coinciding with the threshold voltage. And we obtained the fully-driving property which prevents the particle lumping and decides the image quality and lifetime of panel from the optical characteristics and occupation surface of moving particles.

• Journal of the Optical Society of Korea
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• 제18권2호
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• pp.101-109
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• 2014

In this paper, four apodization functions are proposed for silicon-on-insulator (SOI) strip waveguides with sidewall-corrugated gratings. The effects of apodization functions on the full width at half maximum (FWHM), the side-lobe level, and the reflectivity of the reflection spectrum are studied using the coupled-mode theory (CMT) and the transfer-matrix method (TMM). The results show that applying proposed apodization functions creates very good filtering characteristics. Among investigated apodized waveguides, the apodization functions of Polynomial and z-power have the best performance in reducing side-lobes, where the side-lobe oscillations are entirely removed. Four functions are also used for precise adjustment of the bandwidth. Simulation results show that the minimum and maximum values of the FWHM are 0.74 nm and 8.48 nm respectively. In some investigated functions, changing the apodization parameters decreases the reflectivity which is compensated by increasing the grating length.

• Journal of the Optical Society of Korea
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• 제13권4호
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• pp.423-427
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• 2009

The results of the experimental and theoretical studies conducted on terahertz filtering using two parallel-plate waveguides (PPWGs) are presented herein. The first PPWG with 355 ${\mu}m$ plate separation generates 4 THz bandwidth TM modes ($TM_0,\;TM_2,\;and\;TM_4$), whereas the second PPWG with 100 ${\mu}m$ plate separation operated the THz filter for the generated TM modes with 1.5 THz cutoff frequency. The outgoing THz wave of the two PPWGs was truncated until 1.5 THz, and the system was operated using a high-pass THz filter. The absorption and dispersion of the combined TM and TE modes for the filtering system were calculated. The theoretical calculation and measurement results for the cutoff and oscillation frequency in the spectrum domain agreed well.

• Journal of the Optical Society of Korea
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• 제11권3호
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• pp.130-132
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• 2007

The characteristics of $S\breve{o}lc$ filters in $X^{(2)}$ nonlinear photonic crystals, periodically poled lithium niobate ($LiNbO_3$), were investigated by the Jones matrix method. The transmittance increases and the full width half maximum of the filter becomes narrow as the duty ratio increases. However, the filtering wavelength does not change. The transmittance at the filtering wavelength is over 95% when the duty ratio is larger than 0.35.

• Journal of the Optical Society of Korea
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• 제14권2호
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• pp.104-108
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• 2010

We proposed an axis transformation technique which reveals a distance parameter directly from optical scanning holography (OSH). After synthesis of a real-only spectrum hologram and power fringe adjusted filtering, we transform an original frequency axis to a new frequency axis using interpolation. In the new frequency axis, the filtered hologram has a single frequency which is linearly proportional to the distance parameter. Thus, the inverse Fourier transformation of the filtered hologram gives a delta function pair in the new spatial axis. Finally, we extract the distance parameter by detecting the location of the delta function pair.

• 한국전기전자재료학회논문지
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• 제16권12S호
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• pp.1261-1267
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• 2003

Since the grating optical low-pass fillet degrades the resolution of images, we developed a hologram optical low-pass filter that show low degradation of the image and studied its characteristics. We designed the hologram that divides input beam into circular shaped 21 beams with a Monte-Carlo based hologram generation program and calculated its MTE characteristics to compare it with that of a grating filter. The hologram was manufactured through the optical lithography process and attached to a digital imaging device (Zoran 732212) for measurement. The moirfiltering is compared with zone plate images and the resolution loss is measured with USAF resolution chart. The hologram optical low-pass filter showed better characteristics in both moly filtering and resolution.

• 한국통신학회논문지
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• 제39C권6호
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• pp.476-481
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• 2014

본 논문에서는 가시광 통신의 광원으로 사용되는 백색 LED (Light Emitting Diode)의 변조 대역폭 확장을 위해 송신단에 전치 등화기 회로를 설계하였다. 또한 청색 광 필터를 이용하여 백색 LED의 주파수 응답을 저해하는 황색 형광물질의 영향을 제거하였고 이로 인해 발생하는 신호 세기의 저하를 광학 설계를 통해 극복하였다. 이 시스템을 통해 백색 LED의 변조 대역폭을 결정하는 3 dB 대역폭을 3 MHz에서 25 MHz이상으로 향상 시켰으며 광학 설계를 통해 추가적인 신호 세기를 확보하여 전송 거리를 증가시켰다. 통신 성능 확인을 위해 LED에 NRZ-OOK (신호를 변조시켜 전송하여, APD (Avalanche Photo Diode)를 통하여 수신하였고 이를 CSA (Communication System Analyzer)와 RFSA (Radio Frequency Spectrum Analyzer)를 통해 분석하였다. 이를 통해 전치 등화기와 광학 설계를 이용하여 전송거리 4.5 m에서 30 Mbps, 1.5 m에서 50 Mbps의 신호 전송이 가능함을 실험적으로 검증하였다.

• 한국광학회:학술대회논문집
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• 한국광학회 2003년도 제14회 정기총회 및 03년 동계학술발표회
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• pp.94-95
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• 2003

광학식 3차원 형상측정 기술은 산업현장과 의료분야 등에서 광범위하게 사용되어지고 있으며, 이에 대한 연구도 활발히 진행되고 있다. 본 연구에서는 푸리에 변환법에 의한 위상정보 추출 기술을 개발하고, 주파수 영역에서의 창함수 필터에 따른 위상추출 특성을 분석하였다. 광조사 장치로는 LCD 프로젝터를 이용한 투영방식(그림 1)과 레이저 간섭계 투영방식(그림 2)을 사용하였다. (중략)

• 한국광학회:학술대회논문집
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• 한국광학회 2001년도 제12회 정기총회 및 01년도 동계학술발표회
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• pp.216-217
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• 2001

광섬유와 평면 도파로를 결합한 도파로 구조에서 광 결합 현상은 다양한 응용 가능성 때문에 이론적으로 또는 실험적으로 많은 연구가 되어오고 있다. 광섬유는 단일모드를 이용하고 적당한 곡률이 주어진 블록에 고정한 후 연마하여 클래딩의 일부를 제거하고, 그 상부에 다중모드 평면 도파로(Multi-Mode Overlay Waveguide; MMOW)를 구성한다. 제작된 결합기 구조에서 평면 도파로는 광섬유의 감쇠장 결합(Evanescent field coupling)을 유도하게 되므로, 소자의 특성은 평면 도파로의 구조와 조건에 의해 결정된다. (중략)