• Title/Summary/Keyword: Gratings

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Tunable and switchable multi-wavelength erbium-doped fiber ring laser (파장변환과 스위칭이 가능한 다파장 어븀 첨가 광섬유 링 레이저)

  • Jang, Hyun-Soo;Lee, Kyung-Shik
    • Journal of the Institute of Electronics Engineers of Korea SD
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    • v.42 no.7 s.337
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    • pp.13-20
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    • 2005
  • We propose an erbium-doped fiber ring laser whose multi-wavelength oscillation is tunable and switchable by tuning fiber bragg gratings. By applying axial pressure on the fiber bragg grating, the wavelength spacing of the proposed laser can be tuned continuously. And by adjusting a polarization controller(PC), the proposed laser can be switched among dual-, triple- and four-wavelength lasing operations.

Point Spread Function of Optical Systems Apodized by Semicircular Array of 2D Aperture Functions with Asymmetric Apodization

  • Reddy, Andra Naresh Kumar;Sagar, Dasari Karuna
    • Journal of information and communication convergence engineering
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    • v.12 no.2
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    • pp.83-88
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    • 2014
  • The simultaneous suppression of sidelobes and the sharpening of the central peak in the process of diffraction pattern detection based on asymmetric apodization have been investigated. Asymmetric apodization is applied to a semicircular array of two-dimensional (2D) aperture functions, which is a series of 'coded-phase arrays of semicircular rings randomly distributed over the central circular region of a pupil function' and is similar to that used in the field of diffractive optics. The point spread function (PSF) of an imaging system with asymmetric apodization of the discrete type has been found to possess a good side with suppressed sidelobes, whereas its bad side contains enhanced sidelobes. Further, the diffracted field characteristics are obtained in the presence of these aperture functions. Asymmetric apodization is helpful in improving the performance of the optical gratings or 2D arrays used in real-time imaging techniques.

Characteristics of the diffraction grating formation for SeGe (SeGe 재료의 회절 격자 형성 특성)

  • Park, Jeong-Il;Park, Jong-Hwa;Kim, Jin-Woo;Yeo, Cheol-Ho;Lee, Young-Jong;Chung, Hong-B.
    • Proceedings of the KIEE Conference
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    • 2001.07c
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    • pp.1445-1447
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    • 2001
  • We have investigated about the grating formation of the $a-Se_{75}-Ge_{25}$ chalcogenide thin films. In this study, holographic gratings have been formed by using He-Ne laser(632.8nm) with different polarization states(linear, circular polarization). The diffraction efficiency was obtained by +1st order intensity of the diffracted beam. We have obtained maximum efficiency for Ag-doped thin film. It is observed the difference of the diffraction efficiency with polarization states. S:S-polarized state is shown high efficiency than the other polarization.

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VHOE-based Multi-view Stereoscopic 3D Display System (VHOE광학판을 이용한 다시점 스테레오 입체영상 디스플레이 시스템)

  • Cho, Byung-Chul;Koo, Jung-Sik;Kim, Seung-Cheol;Kim, Eun-Soo
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2002.04b
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    • pp.42-44
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    • 2002
  • The experimental model of the 8-view stereoscopic display system using the photopolymer-based VHOE is proposed. At first, the VHOE is implemented by angle-multiplexed recording of 8-view's diffraction gratings using the optimized exposure-time scheduling scheme in the photopolymer (HRF-150-100) and then. the VHOE-based 8-view stereoscopic display system is implemented by sequentially synchronizing the incident angles of the reference beam of the VHOE with the 8-view stereo images on the LCD pannel. Accordingly, from some experimental results using 8-view images generated by the toed-in stereo camera system, it is found that 8-view stereo images can be diffracted to eight different directions time-sequentially and there is some disparity between the stereo images.

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Optimized Exposure-time Scheduling scheme for Implementation of the Photopolymer-based Multiview VHOE (포토폴리머 기반의 다시점 VHOE 광학판 구현을 위한 최적 노출시간 스케줄링 기법)

  • Kim, Seung-Cheol;Koo, Jung-Sik;Cho, Byung-Chul;Kim, Eun-Soo
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2002.04b
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    • pp.132-135
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    • 2002
  • In this paper, a new method to implement the photopolymer-based VHOE using the optimized exposure time schedule is proposed. The cumulative grating strength dependence on the exposure energy is mathematically modeled by using the fourth-order polynomial function and then using this model, the optimized exposure-time schedule of the photopolymer for recording the given multiple gratings is calculated.

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Diffraction Efficiency Properties of Holographic Gratings by the Reversal Bleached on the Effect of Superadditivity (초부가성 효과에 의한 반전표백 홀로그래피 회절격자의 회절효율 특성)

  • Lim, Chun-Woo
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.23 no.5
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    • pp.403-407
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    • 2010
  • This paper shows that the diffraction efficiency is influenced by superadditivity for the combination of the different developing agent and concentrations in the reversal bleach applied to the Slavich PFG-01 plate to be used for recording transmission holograms. The four developers based on ascorbic acid in combination with metol, phenidone, hydroquinone respectively, were studied. In diffraction efficiency aspect, the superadditivity effect of mixture of two developing agents is lower than one developing agent developer, AAC in the reversal bleach.

Application of rule based expert system to GDS (Grating automatic Drawing System)

  • Lee, Su-Hyoun;Cho, Tae-Ho
    • 제어로봇시스템학회:학술대회논문집
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    • 2002.10a
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    • pp.120.6-120
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    • 2002
  • This paper presents an application of rule based expert system to GDS. Expert system is a computer-based system that uses knowledge, facts, and reasoning techniques to solve problems that normally require the abilities of human experts. Expert system can be classified as synthesis expert system, classification expert system or combination of these. The Expert system of GDS belongs to the synthesis type of expert system. GDS is a graphic design environment that automates complex and time consuming processes in the design phase of the grating production. There are methodical procedures in the design phase of gratings and each process needs the know-how of a skillful designer. User has to know...

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Fabrication & Characterization of Grating Structures for Long Wavelength DFB-LD Using Electron Beam Lithography (전자선 묘화를 이용한 장파장 DFB-LD용 격자 구조의 제작 및 특성 분석)

  • 송윤규;김성준;윤의준
    • Journal of the Korean Institute of Telematics and Electronics A
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    • v.32A no.1
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    • pp.200-205
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    • 1995
  • The 1st and 2nd-order grating structure for long wavelength DFB(Distributed FeedBack) laser diodes are successfully fabricated on InP substrates by using electron beam lithography and reactive ion etch techniques, and also characterized non-destructively by diffraction analysis without removal of photo-resis layer. A new composite layer made by lifted-off Cr layer on thin SiO2 film is developed and used as an etch mask, because PMMA, the e-beamresist, is unsuitable for reactive ion etch of InP. In addition, it is experimentally confiremed that diffraction analysis makes it possible to predict the grating parameters, and the analysis can be used as a non-destructive on-line test to prevent incomplete gratings from being successively processed.

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A neural network extracting the induced stimuli for the perception of subjective contours (주관적 윤각 인식을 위한 유도 자극 추출 신경망)

  • 정은화;홍경호;김욱현
    • Journal of the Korean Institute of Telematics and Electronics C
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    • v.34C no.3
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    • pp.37-47
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    • 1997
  • Human observers perceive a contour where no line or edge is given (subject contour), such as the border between gratings of thin lines offset by half a cycle. Subjective contours occur in a wide variety of circumstances in nature. A common factor in all such figures in the perception of a surface(contour) occuluding part of a background, i.e. subject contours are always accompanied by subject surfaces. Some examples about these kinds of figures are given by kanizsa trangle or square. Ph;ysiological observations are reported in which the perceptual phenomenon that some simple examples of subject contours are perceived as images (gigures; contours) through physiological experiments was investgated. In this paper, we proposed a neural network extracting the induce dstimuli for the perception of subject contours based on the visual mechnism. This visual mechnism is proposed by hubel & wiesel's paper.

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An Asymmetric Sampled Grating Laser and Its Application to Multi-Wavelength Laser Array

  • Ryu, Sang-Wan;Kim, Je-Ha
    • ETRI Journal
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    • v.24 no.5
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    • pp.341-348
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    • 2002
  • We propose an asymmetric sampled grating laser and a multi-wavelength laser array associated with it. Asymmetric sampling periods combined with an index shifter make it possible to use first order reflection for lasing operations. With the structure of our design, we achieved a simple fabrication procedure as well as a high yield without using complex and time-consuming e-beam lithography for multi-period gratings. We analyzed the effect of mirror coating by numerical analysis to improve single mode and power extraction performance. By using high reflection-antireflection coatings, we obtained high power extraction efficiency without degradation of the single mode property. For the multi-wavelength laser array, to gain wavelength control, we varied the sampling periods from one laser to an adjacent laser across the array. With this approach, we showed the feasibility of an array of up to 30 channels with 100 GHz wavelength spacing.

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