• Korean Journal of Optics and Photonics
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• v.14 no.3
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• pp.224-229
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• 2003

We realized a depolarizer based on two 2$\times$2 directional couplers and single mode optical fiber. A reduction method for the degree of polarization is demonstrated by using computer simulation, which is verified experimentally. The degree of polarization is -20 dB for the polarized input beam of spectral width less than 0.05 nm. The experimental results verify that the polarization noise, which is due to the change of the input polarization state, can be reduced by making the fiber-ring delay-line length greater thanthecoherencelengthofthesource.

• Korean Journal of Optics and Photonics
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• v.19 no.2
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• pp.150-158
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• 2008

The exact transmission coefficients at the interface between a uniaxial anisotropic medium and an isotropic medium at? oblique incidence are derived by applying the extended Jones matrix method. When the birefringence of the uniaxial anisotropic medium is small ($|n_e-n_o|\;{\ll}\;n_o,\;n_e$), the exact transmission coefficients are compared with those by the conventional extended Jones matrix method by Yeh et al. They showed an excellent agreement with each other. In addition, using the exact transmission coefficients, we calculated the polarization characteristics of a light through a uniaxial medium to an incident light with arbitrary polarization state at? oblique incidence. We compared the transmittances of an unpolarized light through a pair of crossed o-type polarizers by two different methods and calculated the transmittance as the variation of the optical constants of the polarizers to evaluate of the extinction ratio. The polarization analysis method using the exact transmission coefficients can be applied to polarization characteristics of a light through a uniaxial medium with large birefringence as well as to liquid crystals and to optical anisotropic material.

• Korean Journal of Optics and Photonics
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• v.15 no.2
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• pp.142-148
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• 2004

We investigated a Ti:LiNbO$_3$ based integrated-optic polarization controller with a Ti-indiffused waveguide along the z-axis utilizing the electro-optic effect. The device consists of a first quarter-wave (λ/4) phase-shifter followed by a half-wave(λ/2) and a second quarter-wave(λ/4) wave-plate, which is rotated synchronously with the first quarter-wave phase-shifter. We analyzed the operation principles of the device utilizing cascaded transfer matrices based on Jones matrix and Poincare sphere, simulated driving voltages for various input states of polarization (SOP), and theoretically confirmed transformations from any arbitrary input SOP into any general output SOP.

• Proceedings of the Optical Society of Korea Conference
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• 2004.07a
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• pp.118-119
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• 2004

• Journal of the Korean Chemical Society
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• v.23 no.5
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• pp.314-319
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• 1979

The electronic spectrum of marine dinoflagellate antenna pigment, peridinin, has been described in terms of PPP SCF MO CI computations and fluorescence polarization of the peridinin component in photosynthetic pigment complex of Amphidinium carterae. The main absorption band at 470 nm, $^1B{\leftarrow}A$, is polarized nearly along the long molecular axis. There appear to be two ${\pi}{\rightarrow}{\pi}^*$ transitions (C and $D{\leftarrow}A$) in the socalled "cis" peak region, and they are polarized roughly parallel to the main $B{\leftarrow}A$ absorption. In addition, we have found that the carbonyl group undergoes very 1ittle reorganization of the electronic structure in going from the ground to the $^1B$ excited states of peridinin, while the allenic group shows a strong charge transfer tendency in producing an electron-deficient allente allene group in the excited state.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.2B
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• pp.171-177
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• 2002

As speed and capacity of optical communication system increase dramatically, polarization-mode-dispersion compensation(PMDC) becomes a hot issue in these days. In this paper, we introduce a new state-of-polarization (SOP) tracking algorithm that can be used in a PMDC system. The new SOP tracking algorithm is also based on optical heterodyne coherent detection technique like the previous algorithm that we have reported before. However, unlike the previous algorithm, the new algorithm requires only three times of measurement in any circumstances to find the exact SOP information so that it can effectively be applied to PMDC system where very fast and stable operation is indispensible.

• Proceedings of the KIEE Conference
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• 2002.11a
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• pp.46-47
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• 2002

최근 액정을 주입한 속이 빈 광섬유(Hollow fiber)와 주기적인 전극을 이용하여 전기적으로 제어 가능한 장주기 격자에 대해서 보고된 바 있다. 액정의 중요한 특성 중의 하나는 그 광축이 외부의 전기장에 의해 동적으로 재배열된다는 점이다. 또한 액정은 광축에 따라 굴절률이 다른 비등방성 물질이기 때문에 광축의 배열에 따라, 그리고 입사하는 빛의 편광에 따라 그 빛이 느끼는 굴절률이 달라지게 된다. 본 논문에서는 입사하는 빛의 편광에 따른 액정 장주기 광섬유 격자의 특성에 대해 연구하였다. 주기적인 전극의 길이는 3 cm이고 주기는 500 ${\mu}m$ 이다. 액정을 주입한 속이 빈 광섬유의 길이는 15 mm 이다. 입사하는 빛이 이상(extraordinary) 편광 상태일 때 약 6 dB 의 투과 손실을 나타냈으며 그 대역폭은 약 15 nm 이었다. 이 때 외부에서 인가한 전압은 150 V 였다. 입사하는 빛이 정상(ordinary) 편광 상태일 때에는 액정의 유효 굴절률이 외부 전기장에 대해 변하지 않기 때문에 장주기 투과 특성을 얻을 수 없었다.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.3
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• pp.10-18
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• 2003

In this paper, we propose an optical encryption system based on the encryption of information using the phase component of a wavefront and orthogonal polarization in a Mach-Zehnder interferometer. Since the incoherence of the two perpendicularly polarized lights removes interference component, the decrypted image is stable. In encryption process, the original image is converted into an image having random polarization state by the relative phase difference of horizontal polarization and vertical polarization, so we cannot obtain the original information from the random polarization distribution. To decrypt an Image, the random polarization distribution of encrypted image is divided into two orthogonal components, then key image must be placed on vertical path of Mach-Zehnder interferometer. The decrypted image is obtained In the form of intensity by use of an analyzer.

• Proceedings of the KSRS Conference
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• 2006.03a
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• pp.303-306
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• 2006

이 연구에서는 C 밴드 SAR 자료이면서 서로 다른 편광 상태의 자료를 제공할 수 있는 다중 시기 Radarsat-1 자료와 ENVISAT ASAR 자료를 이용한 토지 피복 분류를 수행하였다. 다중 시기/편광 자료로부터 평균 후방산란계수, 시간적 변이도, 긴밀도 등의 특징을 기본적으로 추출하였고, 이외에 상호 비교를 위해 주성분 분석을 이용한 특징 추출을 시도하였다. 특징들을 이용한 분류기법으로는 Random Forests를 적용하였다. 충남 예당평야 일대를 대상으로 사례연구를 수행한 결과, 주성분 분석을 통한 특징과 다편광 자료를 이용하였을 때 분류 정확도가 향상되는 것으로 나타났다.

• Proceedings of the Optical Society of Korea Conference
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• 2003.02a
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• pp.192-193
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• 2003

광학박막은 유리, 플라스틱, 실리콘, 금속 기판 등에서 표면의 반사율, 투과율, 흡수율과 편광상태 등의 광학적 특성을 변화시키기 위해 광학표면에 코팅을 하여 많이 사용하고 있으며, 파장영역으로는 수 nm의 연x선부터 자외선, 가시광선과 수십 $\mu$m의 적외선까지 적용할 수 있고, 광학기기에서는 대부분의 광학부품이 광학적 특성을 증진시키기 위하여 각각의 목적에 맞도록 코팅되어 있다. 광학코팅의 종류로는 단순한 무반사코팅으로부터 고반사코팅, 칼라필터, 간섭필터, 편광분리기코팅, 마이너스필터 등까지 매우 다양하다. (중략)