• Title/Summary/Keyword: THz Electromagnetic Wave

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Terahertz Imaging Using Compact Continuous Wave Sub-Terahertz System (소형 CW Sub-THz 시스템을 이용한 테라헤르츠 이미징)

  • Jang, Jin-Seok;Kwon, Il-Bum;Yoon, Dong-Jin;Seo, Dae-Cheol
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.21 no.4
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    • pp.340-351
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    • 2010
  • This paper presented compact CW sub-THz imaging system using the terahertz transmitter(Tx) that generates 0.34 THz electromagnetic wave based on electronic device. Using 0.34 THz electromagnetic wave generated by Tx, we measured transmitting terahertz wave magnitude and phase information respectively with terahertz receiver(Rx) based on sub harmonic mixer. This paper measured and compared images of several samples to obtain better imaging results by changing time delay and step distance of scanning stage which affect image resolution. Also, through the imaging measurement of various samples, we were able to assure possibility of application of terahertz wave.

Nondestructive Imaging of an Object Using the Compact Continuous-Wave Sub-Terahertz Imaging System (소형 CW Sub-THz 이미징 시스템을 이용한 물체의 비파괴 이미징)

  • Jang, Jin-Seok;Kwon, Il-Bub;Yoon, Dong-Jin;Seo, Dae-Cheol
    • Journal of the Korean Society for Nondestructive Testing
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    • v.30 no.4
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    • pp.352-358
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    • 2010
  • This paper presented compact CW sub-THz imaging system using the terahertz transmitter(Tx) that generating 0.34 THz electromagnetic wave on based electronic device. Using 0.34 THz electromagnetic wave generated by Tx, we transmitted to sample by point by point scan method and measured transmitting terahertz wave magnitude and phase information respectively with terahertz receiver(Rx) based on sub harmonic mixer. This paper measured and compared images of several samples to obtain better imaging results by changing time delay and step distance of scanning stage which affect image resolution. Also, through the imaging measurement of various samples, we were able to assure possibility of application of terahertz wave.

The Coupling Characteristics of THz Electromagnetic Wave using Copper Wire Waveguide (구리선 도파로를 이용한 THz 전자기파의 결합 특성)

  • Jeon, Tae-In;Ji, Young-Bin
    • Korean Journal of Optics and Photonics
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    • v.17 no.3
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    • pp.290-295
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    • 2006
  • The coupling between copper wire and a THz electromagnetic wave is one of the important factors to build up the magnitude and spectrum of a THz wave. We measured a I THz spectrum range THz pulse into a $480{\mu}m$ diameter and 23cm long copper wire waveguide. We measured THz pulses up to $275{\mu}m$ air gap between the end of the copper wire and transmitter or receiver chips. The coupling sensitivity of the transmitter is 3 times bigger than that of the receiver. The THz pulses propagated to air by the end of the receiver-side copper wire tip acting as a transmitter antenna. We confirmed that the THz field concentrates near the copper wire surface by opening the pin hole to the copper wire waveguide.

Terahertz Time Domain Spectroscopy, T-Ray Imaging and Wireless Data Transfer Technologies

  • Paek, Mun-Cheol;Kwak, Min-Hwan;Kang, Seung-Beom;Kim, Sung-Il;Ryu, Han-Cheol;Choi, Sang-Kuk;Jeong, Se-Young;Kang, Dae-Won;Jun, Dong-Suk;Kang, Kwang-Yong
    • Journal of electromagnetic engineering and science
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    • v.10 no.3
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    • pp.158-165
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    • 2010
  • This study reviewed terahertz technologies of time domain spectroscopy, T-ray imaging, and high rate wireless data transfer. The main topics of the terahertz research area were investigation of materials and package modules for terahertz wave generation and detection, and setup of the terahertz system for time domain spectroscopy(TDS), T-ray imaging and sub-THz wireless communication. In addition to Poly-GaAs film as a photoconductive switching antenna material, a table-top scale for the THz-TDS/imaging system and terahertz continuous wave(CW) generation systems for sub-THz data transfer and narrow band T-ray imaging were designed. Dielectric properties of ferroelectric BSTO($Ba_xSr_{1-x}TiO_3$) films and chalcogenide glass systems were characterized with the THz-TDS system at the THz frequency range. Package modules for terahertz wave transmitter/receiver(Tx/Rx) photoconductive antenna were developed.

Magnetic Resonance and Electromagnetic Wave Absorption of Metamaterial Absorbers Composed of Split Cut Wires in THz Frequency Band (THz 대역에서 Cut Wire로 구성된 메타소재의 자기공진 및 전파흡수특성)

  • Ryu, Yo-Han;Kim, Sung-Soo
    • Journal of the Korean Magnetics Society
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    • v.27 no.2
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    • pp.49-53
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    • 2017
  • Metamaterials composed of split cut wire (SCW) on grounded polyimide film substrate have been investigated for the aim of electromagnetic wave absorbers operated in THz frequency band. Reflection loss and current density distributions are numerically simulated with variations of the SCW geometries using the commercial software. The minimum reflection loss lower than -20 dB has been identified at 5.5~6.5 THz. The simulated resonance frequency and reflection loss can be explained on the basis of the circuit theory of an inductance-capacitance (L-C) resonator. Dual-band absorption can be obtained by arrangement of two SCWs of different length on the top layer of the grounded substrate, which is due to multiple magnetic resonances by scaling of SCWs. With increasing the side spacing between SCWs, a more enhanced absorption peak is observed at the first resonance frequency that is shifted to a lower frequency.

Terahertz Imaging Technology and Applications (테라헤르츠 이미징 기술 및 그 응용 분야)

  • Kim, M.G.;Lee, E.S.;Park, D.W.;Choi, D.H.;Lee, I.M.;Shin, J.H.;Kim, Y.H.;Kim, J.S.;Cho, J.C.;Kim, Y.H.;Kwak, D.Y.;Park, K.H.
    • Electronics and Telecommunications Trends
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    • v.36 no.3
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    • pp.97-105
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    • 2021
  • The terahertz wave (THz wave) is a band between infrared and microwaves and is defined as an electromagnetic wave having a frequency of 0.1 to 10 THz band. THz waves have the property of transmitting nonpolar materials, which the visible light cannot be transmitted, such as ceramics, plastics, and paper; and the photon energy is low, such as several meV. For this reason, non-destructive testing equipment based on THz imaging technology can be applied to the industrial field. Recently, THz imaging technology was applied in wide industrial fields, such as automobiles, batteries, food, medical, and security, and being actively studied. In this paper, we describe the research trends of terahertz imaging technology and experimental results. Furthermore, we summarize the recent commercialized terahertz camera. Finally, we present the research results in the field of the human security scanner system.

Guided Wave THz Spectroscopy of Explosive Materials

  • Yoo, Byung-Hwa;Kang, Seung-Beom;Kwak, Min-Hwan;Kim, Sung-Il;Kim, Tae-Yong;Ryu, Han-Cheol;Jun, Dong-Suk;Paek, Mun-Cheol;Kang, Kwang-Yong;Chung, Dong-Chul
    • Journal of electromagnetic engineering and science
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    • v.11 no.1
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    • pp.42-50
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    • 2011
  • One of the important applications of THz time-domain spectroscopy (TDS) is the detection of explosive materials through identification of vibrational fingerprint spectra. Most recent THz spectroscopic measurements have been made using pellet samples, where disorder effects contribute to line broadening, which results in the merging of individual resonances into relatively broad absorption features. To address this issue, we used the technique of parallel plate waveguide (PPWG) THz-TDS to achieve sensitive characterization of three explosive materials: TNT, RDX, and HMX. The measurement method for PPWG THz-TDS used well-established ultrafast optoelectronic techniques to generate and detect sub-picosecond THz pulses. All materials were characterized as powder layers in 112 ${\mu}m$ gaps in metal PPWG. To illustrate the PPWG THz-TDS method, we described our measurement by comparing the vibrational spectra of the materials, TNT, RDX, and HMX, applied as thin powder layers to a PPWG, or in conventional sample cell form, where all materials were placed in Teflon sample cells. The thin layer mass was estimated to be about 700 ${\mu}g$, whereas the mass in the sample cell was ~100 mg. In a laboratory environment, the absorption coefficient of an explosive material is essentially based on the mass of the material, which is given as: ${\alpha}({\omega})=[ln(I_R({\omega})/I_S({\omega}))]m$. In this paper, we show spectra of 3 different explosives from 0.2 to 2.4 THz measured using the PPWG THz-TDS.

Generation of Ultra-Wideband Terahertz Pulse by Photoconductive Antenna (광전도안테나에 의한 광대역테라헤르츠파의 발생특성)

  • Jin Yun-Sik;Kim Geun-Ju;Shon Chae-Hwa;Jung Sun-Shin;Kim Jeehyun;Jeon Seok-Gy
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.54 no.6
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    • pp.286-292
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    • 2005
  • Terahertz wave is a kind of electromagnetic radiation whose frequency lies in 0.1THz $\~$10THz range. In this paper, generation and detection characteristics of terahertz (THz) radiation by photoconductive antenna (PCA) method has been described. Using modern integrated circuit techniques, micron-sized dipole antenna has been fabricated on a low-temperature grown GaAs (LT-GaAs) wafer. A mode-locked Ti:Sapphire femtosecond laser beam is guided and focused onto photoconductive antennas (emitter and detector) to generate and measure THz pulses. Ultra-wide band THz radiation with frequencies between 0.1 THz and 3 THz was observed. Terahertz field amplitude variation with antenna bias voltage, pump laser power, pump laser wavelength and probe laser power was investigated. As a primary application example. a live clover leaf was imaged with the terahertz radiation.

Study of Coherent High-Power Electromagnetic Wave Generation Based on Cherenkov Radiation Using Plasma Wakefield Accelerator with Relativistic Electron Beam in Vacuum (진공 내 상대론적인 영역의 전자빔을 이용한 플라즈마 항적장 가속기 기반 체렌코프 방사를 통한 결맞는 고출력 전자파 발생 기술 연구)

  • Min, Sun-Hong;Kwon, Ohjoon;Sattorov, Matlabjon;Baek, In-Keun;Kim, Seontae;Hong, Dongpyo;Jang, Jungmin;Bhattacharya, Ranajoy;Cho, Ilsung;Kim, Byungsu;Park, Chawon;Jung, Wongyun;Park, Seunghyuk;Park, Gun-Sik
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.29 no.6
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    • pp.407-410
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    • 2018
  • As the operating frequency of an electromagnetic wave increases, the maximum output and wavelength of the wave decreases, so that the size of the circuit cannot be reduced. As a result, the fabrication of a circuit with high power (of the order of or greater than kW range) and terahertz wave frequency band is limited, due to the problem of circuit size, to the order of ${\mu}m$ to mm. In order to overcome these limitations, we propose a source design technique for 0.1 THz~0.3 GW level with cylindrical shape (diameter ~2.4 cm). Modeling and computational simulations were performed to optimize the design of the high-power electromagnetic sources based on Cherenkov radiation generation technology using the principle of plasma wakefield acceleration with ponderomotive force and artificial dielectrics. An effective design guideline has been proposed to facilitate the fabrication of high-power terahertz wave vacuum devices of large diameter that are less restricted in circuit size through objective verification.

Analysis of the THz Resonance Characteristics of H-shaped Metamaterials with Varying Width

  • Ryu, Han-Cheol
    • 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.