• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.10a
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• pp.290-293
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• 2004

Recently, injection molded plastic optical products are widely used, 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 measuring 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.

• Current Optics and Photonics
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• v.6 no.2
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• pp.129-136
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• 2022

We propose a photonic crystal fiber (PCF) with a slotted porous core and elliptical-hole cladding, for high birefringence in the terahertz regime. Asymmetry in the guided mode is obtained mainly by using arrays of elliptical air holes in the TOPAS^® polymer cladding. We investigate the tradeoff between several structural parameters and find optimized values that can have a high birefringence while satisfying the single-mode condition. The optical properties in the terahertz regime are thoroughly analyzed in numerical simulations, using a full-vector finite-element method with the perfectly-matched-layer condition. In an optimal design, the proposed photonic crystal fiber shows a high birefringence of 8.80 × 10^-2 and an effective material loss of 0.07 cm^-1 at a frequency of 1 THz, satisfying the single-mode-guidance condition at the same time. The proposed PCF would be useful for various polarization-management applications in the terahertz range.

• Journal of the Optical Society of Korea
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• v.19 no.5
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• pp.449-455
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• 2015

In this study we propose a new photonic crystal fiber (PCF) design that simultaneously offers broadband single-mode operation, high birefringence, and large normal dispersion in the optical-communication wavelength regime. The waveguide is based on a hybrid square-lattice PCF (HS-PCF) that has circular air holes of two different diameters alternating in the cladding, plus a pure silica defect at the center. The optical properties of the guided modes are analyzed numerically by the finite-element method (FEM) with a perfectly matched layer as the boundary condition. The optimized HS-PCF has a dispersion coefficient of $-601.67\;ps\;nm^{-1}\;km^{-1}$ and a high birefringence of $1.025{\times}10^{-2}$ at $1.55{\mu}m$. In addition, over the S+C+L+U wavelength bands the proposed HS-PCF with ultraflat birefringence with a slope on the order of $10^{-5}$.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.23 no.11 s.170
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• pp.2050-2057
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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 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 values 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.

• Proceedings of the KSME Conference
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• 2001.06c
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• pp.432-437
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• 2001

It is necessary to improve mechanical and optical porperties in the optical disk substrates as the information storage devices with high storage density using blue laser are being developed. Injection compression molding is regarded as the most suitable process to manufacture optical disk substrates for quality recording and read-out. In the present research, the effects of processing conditions and the insulation layer thickness on gapwise birefringence and the land-groove pattern were investigated. It was found that the values of the birefringence distribution were very sensitive to mold temperature history, and the level of birefringence reduced and, furthermore, the quality of replication was improved due to the insulation layer.

• Design & Manufacturing
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• v.6 no.1
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• pp.90-94
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• 2012

Recently, injection molding process became more popular than ever to produce large quantities of high precision products. Extensive studies have been conducted for reducing the residual stresses and birefringence in injection-molded optical products. Flow-induced and thermally-induced stresses and birefringence have been found as two main sources during injection molding process. Generally, quantitative value of birefringence can be measured with polarizing microscope using the compensator. However, it is difficult to measure low order retardation with microscope, so developing a measurement system for low order optical path difference is in need. In the present paper, a system using Photo Elastic Modulator (PEM) is demonstrated to measure low phase retardation in injection-molded products.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.5 s.176
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• pp.1323-1330
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• 2000

Recently, injection molding process became more popular than ever to produce large quantities of high precision products or optical products. Especially, optical disk that was made by injection mol ding process has been used for many years as a music play media or computer sub-device. The density of data in disk media has been increased continuously. 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 bireffingence structure in injection-molded disks for producing precision injection-molded products. In the present paper 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 bireffingence peaks. But the effect of compression pressure on the bireffingence distribution was found to make the uniform distribution near the center in the gapwise direction. Finally, the value of the birefringence near the wall decreased as the mold temperature increased.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.498-501
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• 2003

We investigated response characteristics of twisted nematic (TN) cell with different nematic liquid crystals (NLCs) and cell gap d on a rubbed polyimide (PI) surface. High transmittance and fast response time of the TN cell on the rubbed PI surface were achieved by using high birefringence (${\Delta}n$) and low cell gap d. The transmittance and response time of the TN cell on the rubbed PI surface decreased with decreasing ${\Delta}nd$. The fast response time of TN cell using high birefringence with ${\Delta}nd=0.363$ on the rubbed PI surface was measured 5.1 ms.

• Current Optics and Photonics
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• v.1 no.6
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• pp.567-572
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• 2017

A novel slotted-core hexagonal photonic crystal fiber (PCF) for terahertz (THz) wave guiding is proposed in this paper. A trade-off managed between effective material loss (EML) and birefringence for efficient guidance of THz waves is illustrated in this article. The rectangular slot shaped air-holes break the symmetry of the porous-core which offers ultra-high birefringence of $8.8{\times}10^{-2}$. The proposed structure offers low bending loss of $1.07{\times}10^{-34}cm^{-1}$ and extremely low effective material loss (EML) of $0.035cm^{-1}$ at an operating frequency of 1.0 THz. In addition other guiding properties such as power fraction, dispersion and confinement loss are also discussed. The proposed THz waveguide can be effectively used for convenient transmission of THz waves.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.11a
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• pp.238-244
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• 2000

FBGs have been extensively used as strain sensors or temperature sensors in a variety of applications related to composites because of embedding ability, small size and multiplexing capability. We inspected embedding environments inside composites with optical fiber by microscope analysis and birefringence characteristics of FBG embedded into textile composite laminate by cure monitoring using a high power WSFL. The cure monitoring of the cases with the striped FBG and the recoated FBG provided comprehensive understandings about the birefringence effect induced by the transverse stress. And these results allowed to consider a recoating method as an important tool to relieve birefringence.