• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.5
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• pp.23-30
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• 2000

To compensate the nonlinearity of electroabsorption modulator(EAM) resulting from its near exponential transfer function, a semiconductor optical amplifier(SOA) that has a log transfer function is used. Since the transfer function of SOA is inverse to that of EAM, the intermodulation distortion(IMD) of EAM can be reduced by cascading SOA to EAM. Also, the RF gain can be increased by the optical gain of SOA. For these reasons, spurious free dynamic range(SFDR) of EAM is enhanced by connecting SOA to EAM in series and operating in gain salutation region. To improve the nonlinearity compensation of EAM, the increased gain of SOA is required and the slope of gain saturation, the ratio of gain to input SOA power, needs to be steep. However, signal spontaneous beat noise that is the dominant system noise increases in proportion to the gain such that the SFDR of EAM is reduced. The higher the gain of SOA is, the more ASE is increased. Thus the noise level of system is increased and the following SFDR of EAM is decreased. The slope of gain saturation region and ASE of have trade-off relation and the optimization is achieved at 8㏈ optical gain. 9㏈ enhancement of SFDR of EAM is obtained. This scheme is easy to embody the linear EAM and the integration with three components (DFB-LD, EAM and SOA) offers many merits, such as low insertion loss, low chirping and low polarization sensitivity.

• Journal of the Korean Society of Radiology
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• v.4 no.2
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• pp.27-30
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• 2010

A X-ray optical modulator measures x-ray dose using optical transmissivity ratio change of the liquid crystal cell. To apply in this optical modulator, we made photoconductor films and compared electrical properties of this films in this study. Photoconductors are deposited on ITO glass with $200{\mu}m$ using the percipitation method and print method. I-V test was conducted to alalyze electrical properties of this films and measured darkcurrent and SNR was acquired using the measured dark current and sensitivity. As a result of this measurements, $HgI_2$ film made by precipitation method is lower(about 40%) darkcurrent than $HgI_2$ films made by precipitation method and sensitivity is two times greater than print method. And we knew that $HgI_2$ films were also 10~25 times greater SNR at $1v/{\mu}m$ than $PbI_2$, PbO, CdTe film made by precipitation method. This results suggest that $HgI_2$ films made by precipitation method has improved characteristics of x-ray dose meter by applying in x-ray optical modulator.

• Proceedings of the Optical Society of Korea Conference
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• 1990.02a
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• pp.264-268
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• 1990

A guided-wave electro-optic Mach-Zehnder interferometric modulator was fabricated on X-cut LiNbO3 . The channel waveguides were formed by proton diffusion with self-aligned SiO2-cladding. A mach-Zehnder interferometric modulator with arm lengths of 7mm has been fabricated and tested at 0.6328${\mu}{\textrm}{m}$. Its modulation depth with V$\pi$ of only 3.5V was 85% and the 3dB bandwidth was 1.6KHz. For high speed operation, the electrode dimension should be reduced to have smaller R, L, and C.

• Proceedings of the Optical Society of Korea Conference
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• 1990.02a
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• pp.269-273
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• 1990

The proton conserving effect of diffusion with self-aligned SiO2-cladding is investigated by infrared transmission spectra. Based on the proton conserving effect, proton-diffused channel waveguides with self-aligned SiO2-cladding substrates. And an electro-optic cutoff modulator with self aligned electrode that utilizes a single-mode proton-diffused channel waveguide in a Y-cut XX-propagating LiNbO3 substrate is fabricated. Over 20 dB extinction has been achieved with applied voltage of 15V.

• Proceedings of the Optical Society of Korea Conference
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• 2002.07a
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• pp.192-193
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• 2002

지금까지 측면이 코어 가까이 연마된 잔일모드 광섬유와 평면 도파로 사이의 광결합을 이용한 소자들이 많이 연구되고 있다. 이를 이용한 소자들로는 광필터, 광변조기, 광스위치, 굴절계, 편광기 등이 있으며 최근에는 파장분할다중화(WDM)에서 인접채널간의 채널분리를 위한 소자로서 빗살필터의 연구 또한 활발히 이루어지고 있다. 이에 본 논문에서는 측면이 코어 가까이 연마된 단일모드 광섬유와 평면도파로 사이의 광결합을 이용한 빗살필터를 제작하였으며 열광학 효과를 이용하여 파장 가변 빗살 필터를 구현해 보았다. (중략)

• Broadcasting and Media Magazine
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• v.16 no.2
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• pp.129-135
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• 2011

Basic principles of kinoform which is a phase hologram, kinoform design using a modified iterative Fourier transform algorithm, and display technology of the kinoform using a spatial light modulator are introduced. Kinoform applications, domestic, and international research trends for those are also introduced.

• Proceedings of the IEEK Conference
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• 1999.06a
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• pp.962-965
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• 1999

We designed and fabricated a travelingwave CPW(coplanar waveguide) electrode for LiNbO$_3$ optical modulator. To Investigate the variation of microwave refractive index of these electrodes, we prepared the CPW electrode samples as a function of electrode thickness and measured the TDR and S-parameter. From this results, we could know the electrode conditions of index matching to 2.20 for 1550nm optical wave index for applying LiNbO$_3$ optical modulator and described. Also, we discussed the some properties of CPW electrode for applying LiNbO$_3$ optical modulator.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.301-304
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• 1999

밀리미터파 대역의 아날로그 광전송을 위한 진행파형 (travel ing wave, TW) 전계흡수 광변조기 (electroabsorption modulator, EAM)와 광수신기의 설계에 대해 발표하고자 한다. TW EAM 및 TW 광수신기의 일반적인 형태인 ridge-type의 co-planar waveguide (CPW)구조에서의 마이크로파의 전송특성을 3차원 FDTD로 분석하여 광파와 전파의 속도 정합 등을 이루는 최적화 구조를 설계하였다. TW EAM의 경우 광세기 변조의 비선형 응답특성에 있어서 마이크로파 손실과 소자길이가 RF 신호의 혼변조 왜곡 (intermodulation distortion)과 SFDR (spurious free dynamic range)성능에 미치는 영향도 이론적으로 조사하였다. TW PIN 광수신기의 경우 광파와 마이크로파의 속도정합의 영향과 이전에는 고려되지 않았던 photo-generated 전송자의 진성 영역에서의 transit time이 광수신기의 밴드 폭에 미치는 영향을 분석하여 최적화 설계하였다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.05a
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• pp.174-174
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• 2004

본 논문에서는 4변이 고정된 정사각형 알루미늄 평판의 진동 진폭을 측정하기 위하여, 기존의 위상 이동 ESP떼 스트로보스코프식 조사를 적용한 스트로보스코픽 ESPI 기법을 이용하였다. 일반적으로 시간평균 ESPI를 이용하면 진동하고 있는 대상체의 정성적인 진동 패턴을 측정할 수 있다. 그러나 시간평균 ESPI로는 진동하고 있는 대상체의 두께방향으로의 진폭량을 측정하기는 어렵다. 또한 일반적인 위상이동법을 적용시킬 경우, 대상체가 진동을 하게 됨으로써 정확한 진동 진폭을 측정하기 어렵다.(중략)

• Proceedings of the Optical Society of Korea Conference
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• 2001.02a
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• pp.212-213
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• 2001

액정은 낮은 전압에서 액정 방향자의 변화에 따른 굴절률 변조를 일으키고 가시광과 근적외선 파장에서 큰 투과도를 가지고 있어 특히 디스플레이 등의 소자에 널리 이용되고 있다. 그러나 현재 액정만을 이용한 디스플레이 등의 응용제품들은 응답속도, 구동특성으로 인해 대화면 구동이 곤란하고 편광판의 사용으로 시야각은 물론 빛 손실량이 크다는 단점과 광변조기로의 응용에 있어서는 큰 파장의존성이 있어 다중 파장의 빛 조절이 어렵고, 또한 입사편광을 왜곡한다는 단점을 가지고 있다. (중략)