• Title/Summary/Keyword: Diffracted light

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A study on the wavelength dependence of the diffracted light (회절된 빛의 파장 의존도에 관한 연구)

  • Kim, Ho-Wook;Lee, Hyuk
    • Proceedings of the KIEE Conference
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    • 1993.11a
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    • pp.365-367
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    • 1993
  • The wavelength dependence of the diffracted light in volume hologram is important in application of volume hologram, because the wavelength dependence of the diffracted light can be used to select a certain wavelength from white-light which is composed of a lot of wavelengths. Some experiments are done to analyze the wavelength dependence of diffracted lights. The coupled wave theory is used to make a theoretical approach to this model. Compared with the theoretical result, the experimental result makes a good agreement with it.

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Design Spectrophotometer for Blocking the $2^{nd}$ diffracted Light (2차 회절광 차단을 위한 분광 광도계 설계)

  • 홍영주;곽윤근;김수현
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2004.10a
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    • pp.875-880
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    • 2004
  • Stray light is the light except the light of the analytic wavelength and the source of measurement error of absorbance. Some experimental results showed that diffractive grating is the major factor of stray light in spectrophotometer. Through the ray tracing with the software tool, classified the paths of the diffractive light from grating and found the range of wavelength which reach the exit slit. The quantity of the stray light(0.025%) is more than the minimum limit of stray light(0.01%) of the single monochromator. A novel optical layout design method, which prevent the reflected rays entering the diffractive grating is proposed.

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The acceleration of microscopic particles in the near field diffracted from the fiber end (광섬유의 Near field를 이용한 미세입자의 가속에 관한 연구)

  • Kang, Yong-Hoon;Lee, Hyuk
    • Proceedings of the KIEE Conference
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    • 1993.11a
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    • pp.359-361
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    • 1993
  • The force exerted on particles when the momentum of light is changed at the boundary is used in accelerating particles in the fluid. So far, particles are accelerated by the gaussian beam focused by lenses or microscopic objectives. In this paper, particles arc moved by the light diffracted from the fiber end. And we proposed the possibility of particle acceleration using the fiber end.

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Beyond the Grating Equation: Light Patterns in the Era of Diffractive Optics

  • O′Shea, D.C.
    • Proceedings of the Optical Society of Korea Conference
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    • 2000.02a
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    • pp.1-1
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    • 2000
  • The interaction of light with periodic patterns generates beautiful color patterns and interesting applications. The basic equation for understanding this phenomena is the grating equation. It tells us the angles, relative to a perpendicular to a grating with a specific period, into which light of a specific wavelength will be diffracted. But what it does not tell us is how much light will be directed into the various "orders" of the grating. It was found that by controlling the shape of the diamond point used to cut the periodic structure into the substrate, a traditional grating could be made to direct most of the light diffracted from it into a single order. This type of grating is referred to as a "blazed" grating. (omitted); grating. (omitted)

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TOWARD A NEXT GENERATION SOLAR CORONAGRAPH: DIFFRACTED LIGHT SIMULATION AND TEST RESULTS FOR A CONE OCCULTER WITH TAPERED SURFACE

  • Yang, Heesu;Bong, Su-Chan;Cho, Kyung-Suk;Choi, Seonghwan;Park, Jongyeob;Kim, Jihun;Baek, Ji-Hye;Nah, Jakyoung;Sun, Mingzhe;Gong, Qian
    • Journal of The Korean Astronomical Society
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    • v.51 no.2
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    • pp.27-36
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    • 2018
  • In a solar coronagraph, the most important component is an occulter to block the direct light from the disk of the sun. Because the intensity of the solar outer corona is $10^{-6}$ to $10^{-10}$ times of that of the solar disk ($I_{\odot}$), it is necessary to minimize scattering at the optical elements and diffraction at the occulter. Using a Fourier optic simulation and a stray light test, we investigated the performance of a compact coronagraph that uses an external truncated-cone occulter without an internal occulter and Lyot stop. In the simulation, the diffracted light was minimized to the order of $7.6{\times}10^{-10}I_{\odot}$ when the cone angle ${\theta}_c$ was about $0.39^{\circ}$. The performance of the cone occulter was then tested by experiment. The level of the diffracted light reached the order of $6{\times}10^{-9}I_{\odot}$ at ${\theta}_c=0.40^{\circ}$. This is sufficient to observe the outer corona without additional optical elements such as a Lyot stop or inner occulter. We also found the manufacturing tolerance of the cone angle to be $0.05^{\circ}$, the lateral alignment tolerance was $45{\mu}m$, and the angular alignment tolerance was $0.043^{\circ}$. Our results suggest that the physical size of coronagraphs can be shortened significantly by using a cone occulter.

Subwavelength Focusing of Light From a Metallic Slit Surrounded by Grooves with Chirped Period

  • Yoon Jaewoong;Choi Kiyoung;Song Seok Ho;Lee Gwansu
    • Journal of the Optical Society of Korea
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    • v.9 no.4
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    • pp.162-168
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    • 2005
  • Extraordinary phenomena related to the transmission of light via metallic films with subwavelength holes and grooves are known to be due to resonant excitation and interference of surface waves. These waves make various surface structures to have optically effective responses. Further, a related study subject involves the control of light transmitted from a single hole or slit by surrounding it with diffractive structures. This paper reports on the effects of controlling light with a periodic groove structure with Fresnel-type chirping. In Fresnel-type chirping, diffracted surface waves are coherently converged into a focus, and it is designed considering the conditions of constructive interference and angular spectrum optimization under the assumption that the surface waves are composite diffracted evanescent waves with a well-defined in-plane wavenumber. The focusing ability of the chirped periodic structures is confirmed experimentally by two-beam attenuated total reflection coupling. Critical factors for achieving subwavelength foci and bounds on size of focal spots are discussed in terms of the simulation, which uses the FDTD algorithm.

The Conditions of a Holographic Homogenizer to Optimize the Intensity Uniformity (주기적인 홀로그램을 이용한 레이저 광 세기 균일화기에서 균일도를 최적화하기 위한 홀로그램의 조건)

  • Go, Chun-Soo;Oh, Yong-Ho;Lim, Sung-Woo
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.24 no.7
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    • pp.578-583
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    • 2011
  • We report on the design of a holographic homogenizer composed of a periodic hologram and a condensing lens. If the hologram is periodic, the homogenizer is free from the alignment error of the incident laser beam. Holographic homogenizer also has an advantage of the flexibility in the size of the target beam. We calculated theoretically the Fraunhofer diffracted wave function when a rectangular laser beam is incident on a periodic hologram. The diffracted wave is the sum of sinc functions at regular distance. The width of each sinc function depends on the size of the incident laser beam and the distance between the sinc functions depends on the period of the hologram. We calculated numerically the diffracted light intensity for various ratios of the size of the incident laser beam to the period of the hologram. The results show that it is possible to make the diffracted beam uniform at a certain value of the ratio. The uniformity is high at the central part of the target area and low near the edge. The more sinc functions are included in the target area, the larger portion of the area becomes uniform and the higher is the uniformity at the central part. Therefore, we can make efficient homogenizer if we design a hologram so that the maximum number of the diffracted beams may be included in the target area.

Reproducible fabrication of diffraction gratings using holographic exposure system (홀로그래픽 간섭 노광계를 이용한 회절격자 제작의 재현성 향상)

  • 이동호
    • Proceedings of the Optical Society of Korea Conference
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    • 1989.02a
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    • pp.193-195
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    • 1989
  • A simple fabrication technique of diffraction gratings with short periods is presented. We can see that the monitoring of diffracted light from photoresist gratings during the development process provides optimum conditions for exposure and development processes. With this technique reproducibility and high quality of diffraction gratings is expected.

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Paticle size analyzer using laser diffraction (레이저 회절성을 이용한 입자크기 분포의 계측 및 해석)

  • 남부희;강성귀;유태우;방병렬;지규인
    • 제어로봇시스템학회:학술대회논문집
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    • 1992.10a
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    • pp.81-85
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    • 1992
  • We design a multi-element photo-detector to measure the size of particles using the diffracted light energy distribution. The scattered profile measured by the photodetector is sampled by a 32 channel analog-to-digital converter. A nonnegative least squares analysis translates the light energy distribution into the corresponding unique particle size distribution. The responses of the particle sizing system are studied theoretically and experimentally.

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Analysis of Surface Plasmon Resonance on Periodic Metal Hole Array by Diffraction Orders

  • Hwang, Jeong-U;Yun, Su-Jin;Gang, Sang-U;No, Sam-Gyu;Lee, Sang-Jun;Urbas, Augustine;Ku, Zahyun
    • Proceedings of the Korean Vacuum Society Conference
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    • 2013.02a
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    • pp.176-177
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    • 2013
  • Surface plasmon polaritons (SPPs) have attracted the attention of scientists and engineers involved in a wide area of research, microscopy, diagnostics and sensing. SPPs are waves that propagate along the surface of a conductor, usually metals. These are essentially light waves that are trapped on the surface because of their interaction with the free electrons of conductor. In this interaction, the free electrons respond collectively by oscillating in resonance with the light wave. The resonant interaction between the surface charge oscillation and the electromagnetic field of the light constitutes the SPPs and gives rise to its unique properties. In this papers, we studied theoretical and experimental extraordinary transmittance (T) and reflectance (R) of 2 dimensional metal hole array (2D-MHA) on GaAs in consideration of the diffraction orders. The 2d-MHAs was fabricated using ultra-violet photolithography, electron-beam evaporation and standard lift-off process with pitches ranging from 1.8 to $3.2{\mu}m$ and diameter of half of pitch, and was deposited 5-nm thick layer of titanium (Ti) as an adhesion layer and 50-nm thick layer of gold (Au) on the semiinsulating GaAs substrate. We employed both the commercial software (CST Microwave Studio: Computer Simulation Technology GmbH, Darmstadt, Germany) based on a finite integration technique (FIT) and a rigorous coupled wave analysis (RCWA) to calculate transmittance and reflectance. The transmittance was measured at a normal incident, and the reflectance was measured at variable incident angle of range between $30^{\circ}{\sim}80^{\circ}$ with a Nicolet Fourier transmission infrared (FTIR) spectrometer with a KBr beam splitter and a MCT detector. For MHAs of pitch (P), the peaks ${\lambda}$ max in the normal incidence transmittance spectra can be indentified approximately from SP dispersion relation, that is frequency-dependent SP wave vector (ksp). Shown in Fig. 1 is the transmission of P=2.2 um sample at normal incidence. We attribute the observation to be a result of FTIR system may be able to collect the transmitted light with higher diffraction order than 0th order. This is confirmed by calculations: for the MHAs, diffraction efficiency in (0, 0) diffracted orders is lower than in the (${\pm}x$, ${\pm}y$) diffracted orders. To further investigate the result, we calculated the angular dependent transmission of P=2.2 um sample (Fig. 2). The incident angle varies from 30o to 70o with a 10o increment. We also found the splitting character on reflectance measurement. The splitting effect is considered a results of SPPs assisted diffraction process by oblique incidence.

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