• Current Optics and Photonics
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• v.5 no.1
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• pp.66-71
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• 2021

The resonance characteristics of H-shaped metamaterials, whose widths were varied while keeping the height constant, were investigated in the terahertz (THz) frequency range. The H-shaped metamaterials were numerically analyzed in two modes in which the polarization of the incident THz electric field was either parallel or perpendicular to the width of the H-shaped structure. The resonant frequency of the metamaterial changed stably in each mode, even if only the width of the H shape was changed. The resonant frequency of the metamaterial operating in the two modes increases without significant difference regardless of the polarization of the incident electromagnetic wave as the width of the H-shaped metamaterial increases. The electric field distribution and the surface current density induced in the metamaterial in the two modes were numerically analyzed by varying the structure ratio of the metamaterial. The numerical analysis clearly revealed the cause of the change in the resonance characteristics as the width of the H-shaped metamaterial changed. The efficacy of the numerical analysis was verified experimentally using the THz-TDS (time-domain spectroscopy) system. The experimental results are consistent with the simulations, clearly demonstrating the meaningfulness of the numerical analysis of the metamaterial. The analyzed resonance properties of the H-shaped metamaterial in the THz frequency range can be applied for designing THz-tunable metamaterials and improving the sensitivity of THz sensors.

• 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.

• The Magazine of the IEIE
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• v.36 no.7
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• pp.62-75
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• 2009

테라헤르츠(THz) 대역은 중적외선(mid-IR)과 밀리미터파(millimeter wave) 사이의 증가 주파수 영역으로서, 다른 전자기파 대역에 비하여 개발 및 활용이 극히 미흡하지만 기존의 전자기파로는 얻어낼 수 없는 탁월한 기능, 즉 통신에 필요한 초고속 광대역, 신기능 센싱 및 새로운 영상정보 등을 제공한다. 이러한 THz 기술이 발전함에 따라 초고속 근거리 무선통신과 함께 센싱 및 영상기술은 생화학 및 의료공학적인 검사와 측정 등 여러 분아에 걸쳐 대단한 영향을 미치고 있다. 그러나 현재의 THz 시스템 기기는 규모가 큰 편이어서 실험실 등 실내 용도로 한정된 상태이다. 이동이 가능한(mobile) 소형화한 THz 시스템은 그 활용범위를 크게 넓힐 수 있으며 새로운 시장을 창출할 수 있다.

• Proceedings of the Optical Society of Korea Conference
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• 2002.07a
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• pp.182-183
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• 2002

최근에 전세계적으로 THz 대역에 관한 연구가 점차 늘고 있는 추세에 있다. THz 대역에서의 연구는 아직까지는 기초적인 학문으로서의 성격이 강하지만 최근의 연구동향을 보면 점차 응용기술으로서의 중요성도 함께 강조되고 있는 경향을 보이고 있다 THz파 대역은 전통적인 광학과 마이크로파 대역의 중간에 위치하고 있으며 우리가 흔히 말하는 빛과 전자기파의 성질을 모두 가지고 있기 때문에 매우 흥미로운 연구대상이라고 할 수 있으며 상대적으로 연구가 거의 되어 있지 않은 마지막 주파수 대역이라고 할 수 있다. (중략)

• Journal of the Korean Society for Nondestructive Testing
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• v.34 no.1
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• pp.68-76
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• 2014

최근 들어 급격히 발전한 테라헤르츠파 발생/검출 기술에 힘입어 생명, 화학, 기계, 통신 등의 다양한 분야에서 THz 관련 응용 연구가 진행되고 있다. 본 강좌에서는 최신 THz 발생/검출 기술을 분야별로 살펴보고 바이오, 재료, 기계 분야의 비접촉식 비파괴검사 분야에 적용 개발되고 있는 THz 기술에 대하여 기술하고자 한다. 특히, 구조물의 THz 비파괴검사 평가 분야 세부 기술에 대하여 자세하게 소개한다.

• Korean Journal of Optics and Photonics
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• v.31 no.1
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• pp.31-36
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• 2020

We propose a band-switchable terahertz metamaterial based on an etched vanadium dioxide (VO₂) thin film. A line of etched VO₂ thin film was placed in the center gap of the split square-loop shape for the tunability of the metamaterial. The resonance frequency of the metamaterial can be switched from the 1.4 THz band to the 0.7 THz band, according to the insulator-metal phase transition in the VO₂ thin film. The absolute difference in the transmittance of the metamaterial was 78.5% and 65.8% at 0.7 THz and 1.4 THz respectively, according to the band switching. The differential phase shift was around 90°, and the transmittance was stably maintained between 40% and 60% in the middle band of the two switchable resonance-frequency bands.

• Journal of Communications and Networks
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• v.16 no.3
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• pp.305-310
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• 2014

Optimal position of access point (AP) is important for multi-gigabit wireless transmission in terahertz (THz) wireless local area network (WLAN)-type applications, where there exist the THz characteristic multiple clusters in channel propagation. By considering the multiple clusters in THz indoor communications, this paper investigates the optimal AP position when two APs are issued for increasing the system capacity. Numerical results reveal that the central position of each AP within each half service region, which offers the shortest cumulated path length for line-of-sight paths, is optimal to achieve the maximal system capacity.

• Korean Journal of Optics and Photonics
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• v.12 no.1
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• pp.1-4
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• 2001

Via terahertz (THz) reflection radar, the characterizations of reflected THz electromagnetic pulses are reported. Quasi-optical techniques are used to efficiently reflect pulses of THz electromagnetic radiation from an aluminum mirror and several conducting and nonconducting materials. An incident THz pulse is reflected up to 9 times to know the magnitude change of a reflected pulse from the aluminum mirror. Using this method, aluminum board, undoped silicon, quartz, and LDPE samples' reflection coefficient and index of refraction can be measured. These results suggest a possible application of transient THz reflection spectroscopy without surface contact.ontact.

• 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 Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.78-79
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• 2005

We report on optically excited terahertz (THz) omission from low-temperature (LT) grown GaAs. We have used 70 fs titanium-sapphire laser pulses with wavelengths at 800 nm to generate THz radiation pulses. The LT-GaAs layers are grown on semi-insulating GaAs substrates with GaAs buffer layer by molecular beam epitaxy (MBE). The THz emission from the LT-GaAs surface is strong and does not show any significant variation in the strength of the THz emission over several different angles between the polarization of the excitation laser pulse and the crystallographic orientation of the LT-GaAs.