• 한국통신학회논문지
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• 제22권1호
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• pp.89-95
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• 1997

X-cut y-propagation $LiNbO_{3}$ 광변조기를 해석하고, 광대역 변조특성을 얻기 위한 설계조건을 구한다. 먼저, 구성된 전극에 대하여 최대 변조효율을 얻기 위한 광도파로의 최적위치를 찾고, 다양한 설계조건에 따른 구동전압, 특성 임피던스, M/W 변조파 유효굴절율을 계산하였으며, 이와 같은 수치적 해석을 위해 유한요소법(FEM: Finite Element Method)을 사용하였다. 그리고 사용된 설계 틀의 유용성을 확인하기 위하여 Becker의 결과와 비교평가 하였다. 본 논문에서는 ridge형 도파로구조의 x-cut $LiNbO_{3}$ 광변조기에 대한 다양한 계산을 통하여, 결과적으로 $1.3{\mu}{\textrm{m}}$의 광신호에 대하여 1.8 V.cm의 구동전압과 특성임피던스 $48.13{\Omega}$ M/W(microwave) 변조파 유효굴절율 2.168을 가치는 x-cut $LiNbO_{3}$ 광변조기를 설계하였다.

• Current Optics and Photonics
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• 제4권4호
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• pp.286-292
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• 2020

Imaging through multicore fiber (MCF) is of great significance in the biomedical domain. Although several techniques have been developed to image an object from a signal passing through MCF, these methods are strongly dependent on the surroundings, such as vibration and the temperature fluctuation of the fiber's environment. In this paper, we apply a new, strong technique called deep learning to reconstruct the phase image through a MCF in which each core is multimode. To evaluate the network, we employ the binary cross-entropy as the loss function of a convolutional neural network (CNN) with improved U-net structure. The high-quality reconstruction of input objects upon spatial light modulation (SLM) can be realized from the speckle patterns of intensity that contain the information about the objects. Moreover, we study the effect of MCF length on image recovery. It is shown that the shorter the fiber, the better the imaging quality. Based on our findings, MCF may have applications in fields such as endoscopic imaging and optical communication.

• Journal of the Optical Society of Korea
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• 제18권6호
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• pp.799-808
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• 2014

The mechanism of optical interaction of two nanoholes, milled in an opaque gold film, by means of surface plasmon polariton (SPP) propagation is investigated. The interaction depends on the polarization direction of the incident light when the nanohole pair is illuminated through uniform single antenna excitations. It is shown that by illuminating one of the nanoholes, under single antenna excitation, the other nanohole can be excited indirectly via propagated SPPs from the excited nanohole. In addition, it is found that the spectrum of electromagnetic power above the surface of the metallic film at an arbitrary point along the axis of the nanohole pair presents two resonant peaks. These peaks are due to the optical interaction between nanoholes, where the short- and long-wavelength peaks can be assigned to in-phase and antiphase interactions of magnetic dipoles relative to each nanohole, respectively. The magnetic coupled dipole approximation (MCDA) method confirms the simulation results.

• 전자공학회논문지D
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• 제35D권7호
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• pp.109-116
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• 1998

In this work was produced and analyzed a z-cut Ti:LiNbO$_{3}$ optical waveguide which applies for various optical devices.A waveguide channel with a thickness 8 .mu.m and a length 66,000.mu.m and a mach-zehnder interferometer type waveguide were fabricated at a diffusion temperature 1050.deg. C for 6-8hours in a wet $O_{2}$ environment. The resulting Ti:LiNbO$_{3}$ optical waveguide was measured to have a Ti-strip thickness of 950.angs. and low loss. Surfaces and cross-sections of a fabricated waveguide were analysed. The mode pattern anaysis revealed that the waveguide showed a single mode at a 1550nm wavelength. The effective dimension of the waveguide was calculated by measuring a gaussian profile; Wx=10.95.mu. and Wy=9.14.mu.m. a propagation loss, of 0.50dB/cm for a TM mode and 0.45dB/cm for a TE mode, was low enough to be accepatable for optical devices.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.111-114
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• 2002

We propose and fabricate a vertically integrated waveguide thermo-optic switch. It controls the optical path between two vertically stacked waveguide. As a first step, we fabricate polymeric waveguides. The measured propagation loss is ranged from 0.3 db/cm to 0.4 dB/cm at the wavelength of 1.55 $\mu\textrm{m}$. We fabricate the proposed vertically integrated waveguide thermo-optic switch to demonstrate its preliminary feasibility. The measured crosstalk is better than -10 db. The power consumption is about 500 mW. Further effort is necessary to improve its performance.

• 한국광학회:학술대회논문집
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• 한국광학회 2001년도 제12회 정기총회 및 01년도 동계학술발표회
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• pp.4-5
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• 2001

Advent of lasers offering high intensity beam has opened the glass to the nonlinear optic (NLO). The high electric field associated with such laser beams can be so large that high order components of the glass polarization can be measured. Such development is of scientific and technological interests in particular in systems involving an intensity-dependent refractive index and/or ultra-fast response (＜10$\^$-12/s). From a scientific viewpoint the NLO response intensity must be understood as a function of the glass composition. On the other hand, large family of applications are presently under investigation in various fields of optical materials or systems e.g. laser glasses for fusion energy, soliton propagation for ultra-long distances, ultra-fast-switching, optical storage etc....(omitted)

• 한국ITS학회 논문지
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• 제8권5호
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• pp.114-120
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• 2009

In outdoor visible light communication channels and LED road illumination communications for the intelligent transport systems (ITS), inter symbol interference (ISI) due to multipath propagation prevents high data rate transmission. Indoor wireless optical communication systems utilizing white LED lights and on the road illumination have been studying about it. Generally, plural lights are installed in room and considered to the traffic information system using existing LED traffic lights. Therefore, their optical path difference must be considered. In this paper, the influence of an optical path difference has been investigated and two approaches against this problem are introduced. One uses on-off keying, return-to-zero (OOK-RZ) coding and the other uses optical orthogonal frequency division multiplexing(OFDM).

• Journal of Information Processing Systems
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• 제10권2호
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• pp.215-222
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• 2014

In this paper, we discuss optical encryption and decryption considering wireless communication channels. In wireless communication systems, the wireless channel causes noise and fading effects of the transmitted information. Optical encryption technique such as double-random-phase encryption (DRPE) is used for encrypting transmitted data. When the encrypted data is transmitted, the information may be lost or distorted because there are a lot of factors such as channel noise, propagation fading, etc. Thus, using digital modulation and maximum likelihood (ML) detection, the noise and fading effects are mitigated, and the encrypted data is estimated well at the receiver. To the best of our knowledge, this is the first report that considers the wireless channel characteristics of the optical encryption technique.

• 한국광학회:학술대회논문집
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• 한국광학회 2002년도 하계학술발표회
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• pp.164-165
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• 2002

광자결정 광섬유(photonic crystal fiber)는 주기적으로 배열된 공기기둥이 광섬유의 길이 방향으로 정렬되어 일반광섬유의 크래팅의 역할을 하고 있고 코어는 이들 공기구멍의 중심부에 인위적인 결함을 만들어 광도파가 가능하게 된다 이러한 광자결정 광섬유의 광학적 특성은 넓은 영역에 걸친 단일 모드 특성, 특이한 모드분산 강한 비선형 등의 기존의 광섬유와는 다른 광특성이 보고되고 있으며 테라 헐즈 펄스 도파가 보고되는 등 그 응용 영역을 넓히고 있다. (중략)

• 대한전자공학회논문지
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• 제26권8호
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• pp.1257-1261
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• 1989

The propagation of electromagnetic waves in a photorefractive crystal is considered. The electromagnetic waves(i.e. TE waves and TM, waves) incident upon the crystal at any incident angle are coupled with reflected waves due to the Fresnel's reflectance in the photorefractive crystal. This coupling leads to a nonreciprocal optical transmissivity. About some incident angles, the optical transmissivity of TE and TM waves in regard to the coupling strength is investigated.