• Applied Chemistry for Engineering
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• v.26 no.3
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• pp.280-286
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• 2015

Two series of unsymmetric dimesogenic compounds containing a butylene or pentamethylene group as the flexible spacer were synthesized and their thermal and mesomorphic properties were studied. Mesogenic groups of the synthesized compounds consisted of a cholesteryl and an azobenzene group with lateral substituent. Chemical structures and mesomorphic properties of the synthesized compounds were investigated by FT-IR, $^1H$-NMR, differential scanning calorimeter (DSC), and polarizing optical microscope (POM). All synthesized compounds, apart from $D5-OCH_3$, showed enantiotropic liquid crystal phases. Compounds having an even number of carbon atoms in the flexible spacer exhibited wide mesophase temperature ranges and high isotropic transition temperatures. Regarding the effect of lateral substituents, compounds with bulky substituents exhibited decreased mesophase temperature ranges and isotropic transition temperatures, while those with polar substituents showed the increased thermal stability of the smectic phase.

• Korean Journal of Optics and Photonics
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• v.7 no.3
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• pp.287-294
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• 1996

An optical phase modulator is fabricated in GaAs/AlGaAs doble heterostructure wafer grown by MOCVD. A self-aligned process, in which the same photoresist pattern is used for both the waveguide etching and the insulation layer formation, is developed and is found to be very useful, Fabry-Perot interference technique is applied to the measurement and the phase modulation efficiency is measured to be 22.5$^{\circ}$/Vmm at 1.31 ${\mu}{\textrm}{m}$ for TE polarization.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.10
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• pp.1-6
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• 2009

We derive the phase error of hologram due to imperfection of a wave plate, the azimuth angle error of a wave plate, and the azimuth angle error of a linear polarizer. Also, we analyze the effect of phase error by the modified triangular interferometer in case of 3-D image reconstruction of hologram.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.7 s.337
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• pp.13-20
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• 2005

We propose an erbium-doped fiber ring laser whose multi-wavelength oscillation is tunable and switchable by tuning fiber bragg gratings. By applying axial pressure on the fiber bragg grating, the wavelength spacing of the proposed laser can be tuned continuously. And by adjusting a polarization controller(PC), the proposed laser can be switched among dual-, triple- and four-wavelength lasing operations.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.326-329
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• 1999

In this paper, we demonstrate a polarization independent optical phase modulator using electro-optic polymer, P2ANS. To overcome the intrinsic polarization dependency of electro-optic effect, we control the optic axis using a new electrode structure. P2ANS(42:75) and P2ANS(25:75) are used for the core layer and the cladding layer, respectively. The buried-type single mode waveguide is fabricated by oxygen ion reactive etching and electic poling is performed by applying 1, 200V at 135$^{\circ}C$. The measured V$_{\pi}$ of the device for both TE and TM modes are 70V.

• Publications of The Korean Astronomical Society
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• v.20 no.1 s.24
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• pp.117-124
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• 2005

We plan to install the polarimetric optics in the AGU(acqusition and guiding unit) of the 1.8 m telescope at the BOAO(Bohyunsan Optical Astronomy Observatory). With this, the spectropolarimetric observations with the resolution of 45,000 and 60,000 in 4,000 to $8,000{\AA}$ ange could be done by the BOES(BOao Echelle Spectrograph). If we use the precision radial velocity measurement capability of the BOES, the accuracy of the magnetic field intensity measurements with this new BOES stokesmeter will be much increased. We present here the design concept of the BOES stokesmeter. Some details on the optics, mechanical parts, fiber parts and the lab test procedures of this stokesmeter are explained.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.12
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• pp.166-172
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• 1995

A novel passive TE/TM polarization mode converter is fabricated by using poled polymer waveguides. The optic axis of the poling induced waveguide is slowly rotated by using a slowly varying structure of poling electrodes. Thus the polarization conversion is achieved as the guided mode propagates through the waveguide. The proposed device is simulated by a full vectorial beam propagation method (VBPM) for anisotropic medium. For the rotation length of 1 mm, the TE polarization of the guided mode is successfully converted to the TM polarization with negligible loss. Based on the simulation results, we fabricated the polarization converter which is tested by using 1.3 $\mu$m laser diode. TE to TM mode conversion is observed with a polarization extinction ratio higher than 30 dB, and the excess loss is less than 1 dB. The polarization conversion is relatively insensitive to wavelength since the device contains no periodic structures. These devices are easier to fabricate than others containing periodic structures.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.148.1-148.1
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• 2014

포항가속기연구소는 Dipole Magnet, Wiggler, Undulator 등 다양한 광원에서 발생되는 강한 방사광을 여러 연구에 이용하고 있다. Max-Planck POSTECH 분원용 타원편광 Undulator (이하, MPK-EPU)는 carbon의 흡수선을 포함하는 250 eV에서 시작하여, 1,500 eV~3,000 eV 에너지 영역의 방사광을 발생시켜 자성물질을 비롯한 다양한 이방성 물질의 연구를 수행하는데 활용할 예정이다. 현재, MPK-EPU용 진공용기의 기계가공, 화학세척, 용접 및 최종 초고진공 진공 달성을 위한 탈기체처리, NEG 활성화 작업등을 마무리하고 PLS-II 저장링 6A 구간에 설치 완료하였다. 이 논문에서는 MPK-EPU용 진공시스템의 제작 및 설치작업에 대한 전반적인 사항과 진공작업 및 그 결과를 발표하고자 한다.

• Proceedings of the Optical Society of Korea Conference
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• 2003.02a
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• pp.164-165
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• 2003

현재의 초고속 인터넷 서비스를 위한 광 인터넷의 기술 확산과 이들의 광통신 가입자망과의 연동으로 가입자 및 Hub 에서의 대규모 광 모듈 수요가 예상되고 있다. 이러한 광 모듈에서 필수적인 소자중의 하나가 파장 여과기이며, 그 수요 충족을 위해서는 소형화와 저가격화가 필수적이다. 이를 만족하기위해 실리카 기반의 다중모드간섭 소자를 이용한 파장 여과기가 개발중에 있다. 하지만, 일반적으로 광소자는 편광에 대한 문제점을 가지고 있기 때문에 이를 고려하지 않으면 출력 도파로에서 효율적인 출력파워를 얻어낼 수 없다. (중략)

• Proceedings of the Optical Society of Korea Conference
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• 1995.06a
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• pp.18-23
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• 1995

광도파로와 반도체 광증폭기를 직접하여 1.3$\mu$m 과장대에서 동작하는 2x2 InGaAsP/InP LD-gate형 광스위치를 제작하였다. 광스위치의 특성으로 광섬유 입출력간의 총삽입 손실이 6~10dB 이었고, 소광비가 40dB 이상으로서 세계적인 수준의 양호한 결과를 얻었다. 제작된 광스위치는 광도파로와 반도체 광증폭기 간의 높은 광 결합 효율을 얻기 위하여 RIE(Reactive Ion Etching) 에 의한 건식 식긱과 4회에 걸친 OMVPE(Organo Metallic Vapor Phase Epitaxy) 결정 성장을 이용하였으녀, 수동 도파로와 LD 사이의 광 결합 효율이 '90% 이상이 됨을 확인하였다. d;라힌 결과는 광집적화의 연구에 상당한 기에를 할 것으로 기대된다.