• Title/Summary/Keyword: High birefringence

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Measurement of Birefringence Distribution in Optical Disk Substrates Fabricated by Injection-Compression Molding (사출압축성형을 통한 광디스크 기판 성형 및 복굴절의 측정)

  • 김종성
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 1999.03b
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    • pp.218-224
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    • 1999
  • It is necessary to improve mechanical and optical properties in the optical disk substrates as the information storage devices with high storage density using short wavelength laser are being developed. Injection compression molding is regarded as the most suitable process to manufacture optical disk substrates with high is regarded as the most suitable process to manufacture optical disk substrates with high dimensional accuracy low residual stresses and superb optical properties In the present study polycarbonate optical disk substrates were fabricated by injection compression molding and the birefringence regarded as one of the most important optical properties for optical disk is measured. The effects of various processing conditions upon the development of birefringence distribution were examined experimentally. It was found that the value of the birefringence distribution were very sensitive to the mold wall temperature history and the variance of the birefringence distribution in the radial direction was affected by the level of the packing and the compression pressure.

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An experimental study on the birefringence and extinction angle distribution in the injection/compression molded optical disk (사출/압축 성형된 광디스크 내의 복굴절 및 광축의 분포에 관한 연구)

  • Kim J. S.;Yoon K. H.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2005.05a
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    • pp.445-448
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    • 2005
  • Recently, injection molding process became more popular than ever to produce large quantities of high precision products or optical products. Injection molding products can cause sensorial problems because of high birefringence or deformation from the residual stresses in the optical media. In the present study, we have focussed on the effect of holding and compression pressures on the optical anisotropy remaining in the MOD by examining the gapwise distribution of birefringence and extinction angle The effect of holding pressure was found to form the inner two birefringence peaks. But the effect of compression pressure on the birefringence distribution was found to make the uniform distribution near the center in the gap-wise direction. Finally, the value of the birefringence near the wall decreased as the mold temperature increased.

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A High Birefringent Polymer Terahertz Waveguide: Suspended Elliptical Core Fiber

  • Wang, Jingli;Chen, Heming;Shi, Weihua
    • Journal of the Optical Society of Korea
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    • v.18 no.5
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    • pp.453-458
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    • 2014
  • A novel high birefringent polymer terahertz (THz) fiber with a suspended elliptical core is proposed in this paper. The introduction of an elliptical core can enhance asymmetry to realize high mode birefringence, and a large porous outer cladding effectively isolates the core-guided mode from interacting with the surrounding environment. A full-vector finite element method(FEM) is used to analyze the characteristics of the THz fiber. Simulation results show that the suspended elliptical fiber exhibits high mode birefringence on a level of $10^{-2}$ over a wide frequency range, and an extremely large mode birefringence(${\approx}0.06226$) is obtained when ellipticity is 0.2. Moreover, a suspended hollow elliptical core fiber is also discussed for the purpose of lower loss, however high mode birefringence and low relative absorption loss can not coexist in such a kind of fiber.

One Image Analysis for 2-D Birefringence Measurements by Chromatic Aberration (색수차를 이용한 2차원 복굴절측정 장치의 개발에 관한 연구)

  • Kim, Jong-Sun;Yoon, Kyung-Hwan
    • Proceedings of the KSME Conference
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    • 2004.04a
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    • pp.1761-1766
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    • 2004
  • Recently, Plastic optical products are widely used. Injection molding process has advantages of low cost and high productivity. However, it remains a residual birefringence and residual stress by difference cooling. The present study focused on measuring birefringence in optical plastic parts using interference color pattern. The main idea of an analysis comes from chromatic aberration which is caused by difference light wavelengths. As a result, a complete system measuring the high order 2-D birefringence pattern was built. Further investigation is under way to improve the accuracy of birefringence measurement system by diode laser.

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An Experimental Study of The Effect of Injection-only and Injection/Compression on The Birefringence Structure in Transparent Disks (사출 및 사출/압축이 투명 디스크의 복굴절 분포에 미치는 영향에 관한 실험적 연구)

  • Min, I.K.;Lee, K.B.;Yoon, K.H.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2009.10a
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    • pp.103-107
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    • 2009
  • Recently, injection/compression molding process became more popular than ever to produce many transparent optical products of high precision. Especially, optical disk for read/write is the best example. But those optical disks can cause sensorial problems because of high birefringence or deformation from the residual stresses in the media. Therefore, it is necessary to study the effects of various process conditions on the final birefringence structure in injection-only and injection/compression molded disks for producing precision injection-molded products. In the present paper we have focused on the effect of injection, holding and compression processes on the optical anisotropy(i.e. birefringence) remaining in the MOD by examining the gapwise distribution of birefringence and extinction angle. The effect of holding pressure was found to form the inner two birefringence peaks. But the effect of compression pressure on the birefringence distribution was found to make the uniform distribution near the center in the gapwise direction and inversion of extinction angle far from the gate.

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Study on Birefringence Effect Of Single-Mode Fiber on Output Spectra of High-Order Fiber Comb Filter Based on Polarization-Diversity Loop Configuration (단일 모드 광섬유의 복굴절이 편광상이 배치구조 기반 고차 광섬유 빗살 필터의 출력 스펙트럼에 미치는 영향에 대한 고찰)

  • Kim, Young-Ho;Lee, Yong-Wook
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.26 no.6
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    • pp.8-15
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    • 2012
  • In this paper, we investigated possible optical parameters causing deviation of experimentally observed output spectra from theoretically predicted results in a high-order fiber comb filter based on a polarization-diversity loop configuration. They include wavelength dependency of half-wave plates (HWPs) inserted in the filter for wavelength switching and the modal birefringence of single-mode fibers (SMFs) with which optical components comprising the filter are connected. In order to consider the effect of the modal birefringence of the SMF on a filter performance, it is modeled as a low birefringence fiber with an arbitrary orientation angle and birefringence. It is found from the simulation results that the modal birefringence of SMFs strongly affects the spectral characteristics of the filter and decreases the extinction ratio of the filter, compared with the wavelength dependency of HWPs. In particular, it is also confirmed that the spectral deviation and asymmetric distortions of side-lobes in narrow band transmission spectra result mainly from the modal birefringence of SMFs.

A Study on the Rotation-Induced Birefringence in Plastic Disk Substrate (회전에 의해 플라스틱 기판에 추가로 발생하는 복굴절의 측정에 관한 연구)

  • 김종선;윤경환
    • Transactions of Materials Processing
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    • v.12 no.8
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    • pp.730-737
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    • 2003
  • Extensive studies have been conducted for reducing the residual stresses and birefringence in injection-molded optical disk substrate Flow-induced and thermally-induced stresses and birefringence have been found as two main sources during injection molding process. However, high speed rotation also induces extra stresses and birefringence in real operation of disk drives. In the present paper rotation-induced in-plane birefringence has been measured and presented for CD and DVD substrates at different radial position. About 10 - 15 nm of extra retardation in one pass has been measured up to 4,800 rpm. The distribution of extra rotation-induced birefringence will be valuable data for designing an optimal optical disk substrate. Finally, experimental results were compared with the extra stresses calculated from simple formulation.

A Study on the Rotation-induced Birefringence in Plastic Disk Substrate (회전에 의한 플라스틱 기판에 야기되는 복굴절의 측정에 관한 연구)

  • 김종선;윤경환
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2003.05a
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    • pp.470-473
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    • 2003
  • Extensive studies have been conducted for reducing the residual stresses and birefringence in injection-molded optical disk substrate. Flow-induced and thermally-induced stresses and birefringence have been found as two main sources during injection molding process. However, high speed rotation also induces extra stresses and birefringence in real operation of disk drives. In the present paper rotation-induced in-plane birefringence has been measured and presented for CD and DVD substrates at different radial position. About 10 - 15 nm of extra retardation has been measured up to 4,800 rpm.

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16.3: Conjugation Effects on High Birefringence Liquid Crystals

  • Catanescu, Carmen Otilia;Lee, Soon-Nam;Chien, L. C.
    • 한국정보디스플레이학회:학술대회논문집
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    • 2003.07a
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    • pp.260-262
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    • 2003
  • We report several difluoro isothiocyanato tolane-based liquid crystal (LC) singles having a high optical birefringence. Several eutectic mixtures are formulatd using these LC singles exhibiting a wide nematic phase range and high birefringence. We will report the physical properties of and photochemical stability of these new eutectic mixtures.

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A Study on the Birefringence Measurement in Injection Molded Parts Using R-G-B Separation of White Light (백색광의 삼파장 분해에 의한 2차원 복굴절측정 장치의 개발에 관한 연구)

  • Yoon Kyunghwan;Kim Jongsun
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.29 no.6 s.237
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    • pp.828-834
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    • 2005
  • Recently, injection molded plastic optical products are widely used in many fields, because injection molding process has advantages of low cost and high productivity. However, there remains residual birefringence and residual stresses originated from flow history and differential cooling. The present study focused on developing a technique to measure the birefringence in optical plastic parts using R-G-B separation of white light. The main idea of an analysis comes from the fact that more information can be obtained from the distribution of retardation caused by different wavelengths. A complete system to give the quantitative values of retardation covering high order 2-D birefringence will be demonstrated. Further investigation is under way to improve the accuracy of the system using diodes as light sources.