• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2006년도 6th International Meeting on Information Display
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• pp.421-421
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• 2006

The light and energy-efficiency of classical liquid crystal displays is notoriously poor due to the use of absorption-based linear polarisers and colour filters. For instance, the light efficiency of PVAL polarisers is typically between 40 and 45 % and the colour filters have a typical efficiency below 35 % which results in a total light and energy-efficiency of the display below 10 %. In the past, a variety of polarizers were developed with an enhanced efficiency in generating linearly polarized light. Typically, these polarizers are based on the polarisationselective reflection, scattering or refraction of light i.e. one polarisation direction of light is directly transmitted to the LCD/viewer and the other polarization direction of light is depolarised and recycled which results in a typical efficiency for generating linearly polarized light of 70-85 %. Also, special colour filters have been proposed based on chiral-nematic reactive mesogens which increase the efficiency of generating colour. Despite the enormous progress in this field, a need persists for improved methods for generating polarized light and colour based on low cost optical components with a high efficiency. Here, the use of holographic phase gratings is reported for the generation of polarized light and colour. The phase grating are recorded in a photopolymer which is coated onto a backor frontlight for LCDs. Typically the recording is performed in the transmisson mode or in the waveguiding mode and slanted phase gratings are generated with their refractive index modulation at an angle between 20o and 45o with the normal of the substrate. It is shown that phase gratings with a high refractive index modulation and a high efficiency can be generated by a proper selection of the photopolymer and illumination conditions. These phase gratings coupleout linearly polarized light with a high contrast (> 100) and the light is directed directly to the LCD/viewer without the need for redirection foils. Dependent on the type of phase grating, the different colours are coupled-out at a slightly different angle which potentially increases the efficiency of classical colour filters. Moreover, the phase gratings are completely transparent in direct view which opens the possibility to use them in frontlights for LCDs. Holographic polarization gratings posses a periodic pattern in the polarization state of light (and not in the intensity of light). A periodic pattern in the polarization direction of linearly polarized light is obtained upon interference of two circularly polarized laser beams. In the second part of the lecture, it is shown that these periodic polarization patterns can be recorded in a linear photo-polymerizable polymer (LPP) and that such an alignment layer induces a period rotation in the director of (reactive and non-reactive) liquid crystals. By a proper design, optical components can be produced with only first order diffraction and with a very high efficiency (>0.98). It is shown that these diffraction gratings are potentially useful in projection displays with a high brightness and energy efficiency

• Journal of Astronomy and Space Sciences
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• 제28권4호
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• pp.267-271
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• 2011

I developed an enhanced correction method for Ricean bias which occurs in linear polarization measurement. Two known methods for Ricean bias correction are reviewed. In low signal-to-noise area, the method based on the mode of the equation gives better representation of the fractional polarization. But a caution should be given that the accurate estimation of noise level, i.e. ${\sigma}$ of the polarized flux, is important. The maximum likelihood method is better choice for high signal-to-noise area. I suggest a hybrid method which uses the mode of the equation at the low signal-to-noise area and takes the maximum likelihood method at the high signal-to-noise area. A modified correction coefficient for the mode solution is proposed. The impact on the depolarization measure analysis is discussed.

• Journal of information and communication convergence engineering
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• 제14권3호
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• pp.163-170
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• 2016

Because of rapid technological advancements, increased data rate support has become the key criterion for future communication medium selection. Multimode optical fibers and multicore optical fibers are well matched to high data rate throughput requirements because of their tendency to support multiple modes through one core at a time, which results in higher data rates. Using the numerical mode solver OptiFiber, we have designed a concentric core fiber by investigating certain design parameters, namely core diameter (µm), wavelength (nm), and refractive index profile, and as a result, the number of channels, material losses, bending losses, polarization mode dispersion, and the effective nonlinear refractive index have been determined. Space division multiplexing is a promising future technology that uses few-mode fibers in parallel to form a multicore fiber. The experimental tests are conducted using the standard second window wavelength of 1,550 nm and simulated results are presented.

• 한국전자파학회논문지
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• 제22권2호
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• pp.228-235
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• 2011

본 논문에서는 위상 배열 시스템에서 활용 가능한 $4{\times}8$ 이중 편파 기판 집적 도파관(SIW: Substrate Integrated Waveguide) 슬롯 배열 안테나를 제안한다. 제안된 배열 안테나는 수직 편파 안테나와 수평 편파 안테나로 구성 되어 이중 편파가 가능하며, 수직 편파 안테나는 기존의 기판 집적 도파관을 이용하여 가로 슬롯 선형 안테나를 배열하였으며, 수평 편파 안테나는 half mode 기판 집적 도파관(HMSIW: Half Mode Substrate Integrated Waveguide)을 사용하여 세로 슬롯 선형 안테나를 배열하였다.

• Journal of Electrical Engineering and Technology
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• 제10권1호
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• pp.331-337
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• 2015

A novel fully-printed microstrip antenna with negative first resonance and dual polarization is proposed. The radiator is printed on the 1-layer substrate instead of multilayers. The -1st resonance results from a composite right- and left-handed(CRLH) structure that has a circumferentially interlocked gap capacitively coupling a patch with a shorted-ring. This compact antenna is provided with a dual-polarization capability by creating two orthogonal linear polarizations in one body with coaxial feeds. The design is carried out by doing full-wave EM field simulation which is compared with the measurement of the fabricated antenna prototype. The measured results give the gain of 5 dBi and the efficiency of 78% at the -1st resonance mode as the center frequency of a downlink channel of the bandwidth over 20 MHz with 29 dB polarization isolation for mobile communication.

• 한국광학회지
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• 제11권3호
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• pp.193-197
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• 2000

음향파 장벽 구조와 음향광학효과를 이용한 편광모드 변환형 파장가변 광 필터를 LiNbo3와 Ti 이중 확산 공정 기술을 이용하여 제작하였다. 1552.6nm 파장의 TE, TM 입사 편광모드에 대해서 173.07MHz, 173.05MHz의 Rf 주파수에서 81% 이상의 변환효율과 ∼200kHz(∼1.83nm)의 통과대역폭을 얻어Tdmaum 구동파워는 10.97mW로서 음향파 장벽이 없는 광 필터 파워의 10%에 불과 하였다. 파장 변화율과 부 모드 레벨리 각각 8.2nm/MHz와 -4dB로 측정하였다.

• 한국전자파학회논문지
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• 제7권3호
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• pp.254-262
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• 1996

본 논문에서는 선편파와 원편파를 상호간에 선택적으로 변환할 수 있는 3단 회전핀으로 구성된 편파기를 설계하였다. 편파기를 설계하기 위해 구형 도파관과 원형 도파관을 결합시켜 모드변환이 원활이 이루어지도록 전송선이론을 적용하였고, 원형 도파관내에 유전체판을 삽입시켜 삽입된 각도에 따라 편파변환을 선택적으로 가능하게 설계하였다. 또한 설계된 데이타를 이용하여 입.출력단에 나타나는 전송특성 및 반사특성이 최적이 되도록 시뮬레이션 하였고, 편파기 제작을 통하여 이론의 타당성을 입증하였다.

• Bulletin of the Korean Chemical Society
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• 제34권10호
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• pp.2895-2899
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• 2013

Direction of intercalation to DNA of the planar dipyrido[3,2-a:2',3'-c]phenazine ligands (dppz) of a bis-Ru(II) complex namely, $[Ru(1,10-phenanthroline)_2dipyrido[3,2-a:2^{\prime},3^{\prime}-c]phenazine]^{2+}$ linkered by a 1,3-bis(4-pyridyl)propane, was investigated by probing the behavior of 4',6-diamidino-2-phenylindole (DAPI) that bound deep in the minor groove. Bis-intercalation of DPPZ resulted in a little blue shift and hyperchromism in DAPI absorption band, and a large decrease in DAPI fluorescence intensity which accompined by an increase in the dppz emission intensity. Diminishing the intenisty of the positive induced circular dichroism (CD) and linear dichroism (LD) were also observed. These spectral changes indicated that insertion of dppz ligand caused the change of the binding mode of DAPI, which probably moved to the exterior of DNA from the minor groove and interacted with the phospghate groups of DNA by electrostatic interaction. At the surface of DNA, DAPI binds at the phosphate groups of DNA by electrostatic attraction. Consequently, this observation indicated that the dppz ligand intercalated from the minor groove.

• Bulletin of the Korean Chemical Society
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• 제31권12호
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• pp.3658-3662
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• 2010

A new bis-Ru(II) complex, in which two [Ru(1,10-phenanthroline)$_2$dipyrido[3,2-a:2',3'-c]phenazine]$^{2+}$ were tethered by a 1,3-bis(4-pyridyl)propane linker, was synthesized and its binding mode and stoichiometry to DNA was investigated by optical spectroscopy including linear dichroism (LD) and fluorescence intensity measurement. The magnitude of the negatively reduced LD signal of the bis-Ru(II) complex in the dipyrido[3,2-a:2',3'-c]phenazine (DPPZ) ligand absorption region appeared to be similar compared to that in the DNA absorption region, which is considered to be a diagnostic for DPPZ ligand intercalation. The binding stoichiometry measured from its LD magnitude and enhanced fluorescence intensity corresponds to one ligand per three DNA bases, effectively violating the nearest neighbouring site exclusion model for classical DNA intercalation. This observation is in contrast with monomer analogue [Ru(1,10-phenanthroline)$_2$dipyrido[3,2-a:2',3'-c]phenazine]$^{2+}$, which is saturated at the DPPZ ligand to DNA base ratio of 0.25, or one DPPZ ligand per four nucleobases.

• Bulletin of the Korean Chemical Society
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• 제31권5호
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• pp.1314-1318
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• 2010

The $[Ru(tpy)_2]Cl_2$ (tpy:2,2':6',2"-terpyridine) complex was synthesized and its structure was confirmed by $^1H$-NMR and elemental analysis. Its binding mode toward DNA was compared with the well-known $[Ru(bpy)_3]Cl_2$ (bpy:2,2-bipyridyl), using isotropic absorption, linear dichroism(LD) spectroscopy, and an energy minimization study. Compared to $[Ru(bpy)_3]^{2+}$, the $[Ru(tpy)_2]^{2+}$ complex exhibited very little change in its absorption pattern, especially in the MLCT band, upon binding to DNA. Furthermore, upon DNA binding, both Ru(II) complexes induced a decrease in the LD magnitude in the DNA absorption region. The $[Ru(tpy)_2]^{2+}$ complex produced a strong positive LD signal in the ligand absorption region, which is in contrast with the $[Ru(bpy)_3]^{2+}$ complex. Observed spectral properties led to the conclusion that the interaction between the ligands and DNA bases is negligible for the $[Ru(tpy)_2]^{2+}$ complex, although it formed an adduct with DNA. This conclusion implies that both complexes bind to the surface of DNA, most likely to negatively charged phosphate groups via a simple electrostatic interaction, thereby orienting to exhibit the LD signal. The energy minimization calculation also supported this conclusion.