• Journal of the Korean Chemical Society
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• v.60 no.1
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• pp.28-33
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• 2016

The spiropyran is a typical material having photodegradation properties in the process of photochromism. The spiropyran has been utilized in various applications such as optical switch, optical memories, and biosensor because of its remarkable stability, fast responsive time, stronger color change, and photo-induced controllability. However, the spriropyran is photodegraded by the repetitive optical irradiation. The photodegradation of spiropyran have been investigated by using UV-Visible spectroscopy, nuclear magnetic resonance (NMR), and Raman spectroscopy. Herein, the properties of spiropyran were characterized by using terahertz time-domain spectroscopy (THz-TDS) in the terahertz frequency region. In terahertz region, the measured absorbance of spiropyran was increased due to the photodegradation induced by the repetitive UV irradiation. The absorbance tendency of spiropyran in the terahertz frequency region was compared with that in the visible region, and they were completely opposite to each other.

• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.2
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• pp.119-124
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• 2008

In recent years, gradually increasing interest has been directed to the use of terahertz technology in nondestructive testing and non-invasive measurements, and terahertz time domain spectroscopy (THz-TDS) has become a key technology in such applications. This paper deals with the terahertz pulse generation from cadmium telluride via optical rectification process of femto-second infrared laser pulses. The measured terahertz spectrum is compared with the result of model calculation based on space-time domain nonlinear Maxwell equations for coherent frequency mixing process. The propagation process of terahertz and infra-red pulses in the material as well as the surface interference and free space diffraction effects are also considered. The experimental results are in good agreements with the calculated spectrum.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.05a
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• pp.303-306
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• 2001

Using THz time-domain spectroscopy (THz-TDS), the power absorption and the real conductivity of silica sand are measured terahertz frequency range. It is impossible to measure the characterization of the silica sand by simple electrical measurements using mechanical contacts, e.g., Hail effect or four-point probe measurements. However, the THz-TDS technique can measure not only electrical but also optical characterization of the sample. Also this technique can measure frequency dependent results. Especially, the real conductivity was increased according to THz frequency this is unusual material compare with metal and semiconductor materials; the measured real conductivity are not followed by the simple Drude theory.

• Proceedings of the Optical Society of Korea Conference
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• 2009.10a
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• pp.123-124
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• 2009

• Electronics and Telecommunications Trends
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• v.21 no.4 s.100
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• pp.129-141
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• 2006

최근의 광-나노 기술의 발전에 힘입어, 테라헤르츠(THz)파 분야에 있어서 기술혁신이 이루어지고 있다. THz 시간영역 분광법, THz-QCL, 서브-THz 무선 통신, 서브-THz전기신호 처리기술 및 THz 디바이스 등 다양한 THz파 관련 연구 성과가 폭넓게 전개되고 있어, 새로운 과학기술 분야의 하나로서, 또 신규산업의 개척을 짊어지는 것으로서 크게 기대되는 기술이다. 따라서 구체적인 장래 전망을 명확히 하기 위하여 THz 기술에 관한 기술동향을 분석하였다. 본 고에서는 기술동향 분석 결과를 토대로 THz파 기술의 현황과 전망에 관하여 설명하고, 차세대 핵심기술(core-technology) 창출을 목표로, THz 전자파, THz-photonics, THz-electronics 세 가지 연구분야의 총합적인 추진을 제안하고자 한다.

• Journal of Sensor Science and Technology
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• v.27 no.5
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• pp.317-327
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• 2018

Terahertz (THz) time-domain spectroscopy(TDS), imaging techniques, and related systems have become mature technologies, widely used in many universities and research laboratories. However, the development of creative technologies still requires improved THz application systems. A few key points are discussed, including the innovative advances of mode-locking energy-emitting semiconductor lasers and better photoconductive semiconductor quantum structures. To realize a compact, low cost, and high performance THz system, it is essential that THz spectroscopy and imaging technologies are better characterized by semiconductor and nano-devices, both static and time-resolved. We introduce the THz spectroscopy and imaging systems, the OSCAT(Optical Sampling by laser CAvity Tuning) system and the ASOPS(ASynchronous Optical Sampling) system, are constructed by our research team. We report on the THz images obtained from their use.