• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1999.11a
• /
• pp.541-544
• /
• 1999

We synthesised a novel photo-alignment material of PCEMA (poly(cinnamolyethyl methacrylate)) on photo-dimerization reaction. Next we investigated the electro-optical (EO) characteristics of photo-aligned twisted nematic (TN)-liquid crystal display (LCD) with linearly polarized ultraviolet (UV) light irradiation on PCEHA surface. The excellent voltage-transmittance characteristics of photo-aligned TN-LCD on PCEMA surface were obtained. The threshold voltage of photo-aligned TN-LCD decreases with increasing the UV light irradiation time on PCEMA surface. Also, the response time of photo-aligned TN-LCD on PCEMA surface is almost the same as rubbing-aligned TN-LCD.

• Bulletin of the Korean Chemical Society
• /
• v.20 no.10
• /
• pp.1186-1194
• /
• 1999

Photoresponsive side chain polymers containing aminonitro azobenzene were synthesized for studying optically induced birefringence. Four different copolymers were prepared using methacrylate, a-methylstyrene, and itaconate monomer. Two copolymers are totally amorphous and the other two are liquid crystalline in nature. Trans-to-cis photoisomerization was observed under the exposure of UV light with UV-VIS absorption spectroscopy. Reorientation of polar azobenzene molecules induced optical anisotropy under a linearly polarized light at 532 nm. The dynamic parameters of optically induced birefringence let us compare the effect of polymeric structure on the rate of growth and decay of the birefringence. Besides the effect of glass transition temperature on the dynamics of photoinduced birefringence, we focused our interests on the geometrical hindrance of polar azobenzene molecules and cooperative motion of environmental mesogenic molecules in the vicinity of polar azobenzene moiety.

• Bulletin of the Korean Chemical Society
• /
• v.21 no.12
• /
• pp.1222-1226
• /
• 2000

We synthesized the simple triethoxysilanes (SGDR1) bearing a disperse red 1 for thin film fabrication. The thin films were prepared using the solution of SGDR1 after hydrolysis and condensation. The films were annealed at two different temperatures such as $150^{\circ}C$ and $200^{\circ}C$. Trans-to-cis photoisomerization was observed under the exposure of 532 nm light with UV-Vis absorption spectroscopy. The kinetic study of photoisomerization was performed in the film. Reorientation of the polar azobenzene molecules induced optical anisotropy under a linearly polarized light at 532 nm. The effect of aggregation of the chromophores and annealing of the silicon oxide in the matrix were studied on the dynamic properties of isomerization and induced birefringence.

• Journal of the Optical Society of Korea
• /
• v.13 no.4
• /
• pp.472-477
• /
• 2009

A Stokes polarimetry imaging (SPI) system was developed and utilized to detect tendon tears by constructing the degree of linear polarization (DOLP) image maps after linearly polarized light illumination. The micro and partial-thickness tears of turkey tendons were made and imaged by the SPI system at different incident polarization angles (IPA) with different mechanical loads on the tendon. The micro and partial-thickness tendon tears were detected by the DOLP images due to weak birefringence around the tears. The tendon tears were detected by a highest DOLP contrast at longest visible wavelength (Red, 650 ${\pm}$ 50 nm). All polarized images showed modulated DOLP as the incident polarization angle (IPA) was varied. The varying DOLP allowed the optimal detection of the micro and partial-thickness tendon tears at a certain IPA. The SPI system with variable IPA and spectral information can improve the detection of the tendon tears by higher visibility of fiber orientations, and thereby improve diagnosis and treatment of the tendon related injuries.

• Journal of Magnetics
• /
• v.11 no.4
• /
• pp.195-207
• /
• 2006

The recently published and new results on design and fabrication of magnetophotonic crystals of different dimensionality are surveyed. Coupling of polarized light to 3D photonic crystals based on synthetic opals was studied in the case of low dielectric contrast. Transmissivity of opals was demonstrated to strongly depend on the propagation direction of light and its polarization. It was shown that in a vicinity of the frequency of a single Bragg resonance in a 3D photonic crystal the incident linearly polarized light excites inside the crystal the TE- and TM-eigen modes which passing through the crystal is influenced by Brags diffraction of electromagnetic field from different (hkl) sets of crystallographic planes. We also measured the faraday effect of opals immersed in a magneto-optically active liquid. It was shown that the behavior of the faraday rotation spectrum of the system of the opal sample and magneto-optically active liquid directly interrelates with transmittance anisotropy of the opal sample. The photonic band structure, transmittance and Faraday rotation of the light in three-dimensional magnetophotonic crystals of simple cubic and face centered cubic lattices formed from magneto-optically active spheres where studied by the layer Korringa-Kohn-Rostoker method. We found that a photonic band structure is most significantly altered by the magneto-optical activity of spheres for the high-symmetry directions where the degeneracies between TE and TM polarized modes for the corresponding non-magnetic photonic crystals exist. The significant enhancement of the Faraday rotation appears for these directions in the proximity of the band edges, because of the slowing down of the light. New approaches for one-dimensional magnetophotonic crystals fabrication optimized for the magneto-optical Faraday effect enhancement are proposed and realized. One-dimensional magnetophotonic crystals utilizing the second and the third photonic band gaps optimized for the Faraday effect enhancement have been successfully fabricated. Additionally, magnetophotonic crystals consist of a stack of ferrimagnetic Bi-substituted yttrium-iron garnet layers alternated with dielectric silicon oxide layers of the same optical thickness. High refractive index difference provides the strong spatial localization of the electromagnetic field with the wavelength corresponding to the long-wavelength edge of the photonic band gap.

• Korean Journal of Optics and Photonics
• /
• v.9 no.3
• /
• pp.129-133
• /
• 1998

The phtocount distributions of a quasi-thermal light source were measured by using the photoelectric counting method. The source was fabricated from the ground glass plate of 9${\mu}{\textrm}{m}$ roughness illuminated by linearly polarized He-Ne laser beam. The coherence time of the quasi-thermal light changed from 31.4$mutextrm{s}$ to 2.48$mutextrm{s}$ according to the grain velocity of the ground glass plate. The photocount distribution showed the Bose-Einstein statistics for a long coherence time compared to the counting time interval, while the distribution approaches the Poisson distribution when the coherence time much shorter than the counting time.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1998.11a
• /
• pp.89-92
• /
• 1998

Amorphous chalcogenide thin films, especially a-(Se, S) based films, exhibit a number of photoinduced phenomena not observed in other types of amorphous thin films. The polarization holographic grating has been formed in amorphous As-Ge-Se-S thin films using two linearly polarized He-Ne laser light. In addition, dffraction efficiency has been measured by the same laser of a relative lower intensity at the same time.

• Journal of Integrative Natural Science
• /
• v.2 no.1
• /
• pp.45-49
• /
• 2009

Electrochemical etching of heavily doped p-type silicon wafers (boron doped, <100> orientation, resistivity; $0.8-1.2m{\Omega}/cm$) with different current density resulting two different refractive indices resulted in DBR (Distributed Bragg Reflectors) porous silicon, which exhibited strong in-plane anisotropy of refractive index (birefringence). Dielectric stacks of birefringent porous silicon acting as distributed Bragg reflectors have two distinct reflection bands depending on the polarization of the incident linearly polarized light. This effect is caused by a three-dimensional (in plane and in depth) variation of the refraction index. Optical characteristics of DBR porous silicon were investigated.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2010.06a
• /
• pp.198-198
• /
• 2010

The low-k SiOCH thin films were prepared by CCP-PECVD method using BTMSM(Bis-trimethylsilylmethane) precursors deposited on p-Si wafer. The structural complexity originate the complex refractive constants of the films, and resulted the elliptical polarization of the incident linearly polarized light source of Xe-ramp in the range from 190nm to 2100nm. Phase difference and amplitude ratio between s wave and p wave propagating through SiOCH thin film was studied. After annealing, the amplitude of p wave was reduced more than s wave, and phase difference between p and s wave was also reduced.

• Journal of Institute of Control, Robotics and Systems
• /
• v.21 no.5
• /
• pp.459-464
• /
• 2015

An on-line quality control of hot steel products is one of the important issues in the steel industry because of cost minimization. In recent years, relative depth information of surface defects is increasingly required for strict quality control. In this paper, a 3D shape reconstruction scheme for defects on a hot steel surface based on a multi-spectral photometric stereo method is proposed. After simultaneously illuminating a hot steel surface by using vertical/horizontal linearly polarized lights of green and blue light sources, the corresponding 4 images are obtained. The photometric stereo method is then applied with the aid of a GPU (Graphic Processing Unit) to reconstruct the shape of the target surface based on these images. The proposed scheme was validated through experiments.