• 한국광학회:학술대회논문집
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• 한국광학회 2009년도 동계학술발표회 논문집
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• pp.359-360
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• 2009

• 한국광학회:학술대회논문집
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• 한국광학회 2009년도 동계학술발표회 논문집
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• pp.181-182
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• 2009

• 한국광학회:학술대회논문집
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• 한국광학회 2009년도 동계학술발표회 논문집
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• pp.185-186
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• 2009

• 한국광학회:학술대회논문집
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• 한국광학회 2009년도 창립 20주년기념 특별학술발표회
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• pp.123-124
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• 2009

• ETRI Journal
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• 제31권6호
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• pp.667-674
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• 2009

Terahertz time-domain spectroscopy has been used to study the optical and dielectric properties of three chalcogenide glasses: $Ge_{30}As_8Ga_2Se_{60}$, $Ge_{35}Ga_5Se_{60}$, and $Ge_{10}As_{20}S_{70}$. The absorption coefficients ${\alpha}({\nu})$, complex refractive index n(${\nu}$), and complex dielectric constants ${\varepsilon}({\nu})$ were measured in a frequency range from 0.3 THz to 1.5 THz. The measured real refractive indices were fitted using a Sellmeier equation. The results show that the Sellmeier equation fits well with the data throughout the frequency range and imply that the phonon modes of glasses vary with the glass compositions. The theory of far-infrared absorption in amorphous materials is used to analyze the results and to understand the differences in THz absorption among the sample glasses.

• 한국전기전자재료학회논문지
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• 제30권11호
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• pp.745-750
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• 2017

Terahertz time-domain spectroscopy has been used to study the optical properties of $Pr^{3+}-doped$ selenide glasses. The complex refractive indexes of $Pr^{3+}-selenide$ glasses were measured in a frequency range from 0.3 to 1.5 THz. The real and imaginary refractive indexes increased with increasing frequency and $Pr^{3+}$ ion concentration. The obtained result indicated that the phonon modes of the $Pr^{3+}-doped$ selenide glasses shift to lower frequencies with the concentration of $Pr^{3+}$ ions. The theory of far-infrared absorption in amorphous materials was used to analyze the results. The measured data showed that the disorder-induced terahertz absorption increased with increasing $Pr^{3+}$ ion concentration.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2001년도 춘계종합학술대회
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• pp.303-306
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• 2001

본 연구는 테라헤르츠 시간영역 분광법 (THz time-domain spectroscopy : THz-TDS)을 이용하여 광학 및 전기 전자 재료로 널리 사용되는 이산화규소의 흡수율과 도전율을 각각 테라헤르츠 주파수 영역에서 측정하였다. 입자 형태로 구성된 이산화규소의 재료는 기존의 접촉식인 Hall 측정이나 4-point probe 측정으로는 그 전기적 특성 분석이 불가능하지만, THz-TDS 방법은 비접촉식 방법으로 전기적 특성뿐만 아니라 광학적 특성 분석도 가능하다. 또한 기존의 전기적 폭정 장치는 DC 영역에서만 가능하지만, 본 방법은 테라헤르츠 주파수 영역에 따른 그 특성을 분석 할 수 있다. 특히 도전율은 금속 및 반도체와 달리 테라헤르츠 주파수가 증가함에 따라 증가하였는데, 이러한 결과는 Drude 이론을 따르지 않음을 확인하였다.

• Journal of Magnetics
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• 제18권2호
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• pp.173-177
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• 2013

Cantilever-detected high-frequency electron spin resonance (ESR) is a powerful method of sub-terahertz and terahertz ESR spectroscopy for a tiny magnetic sample at low temperature. In this technique, a small magnetization change associated with ESR transition is detected as deflection of a sample-mounted cantilever. So far, we have succeeded in ESR detection at 370 GHz using a commercial piezoresistive microcantilever. The spin sensitivity was estimated to ${\sim}10^{12}$ spins/gauss. In order to further increase the sensitivity, we adopt a fiber-optic-based detection system using a Fabry-Perot interferometer in place of piezoresistive system. Fabry-Perot cavity is formed between an optical-fiber end and microcantilever surface, and a change in the interference signal, corresponding to the cantilever deflection, is sensitively detected. This system is suitable for low-temperature and high-magnetic-field experiments because of its compact setup and less heat dissipation. In this study, performance of Fabry-Perot interferometer is evaluated, and its application to cantilever-detected ESR measurement is described.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 추계학술대회 논문집
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• pp.28-28
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• 2007

Ferroelectric $(Ba_{0.5}Sr_{0.5})TiO_3$ (BST) thin films of thickness 500nm were deposited on $LaAlO_3$, (LAO) substrates by at $800^{\circ}C$. BST films were characterized for structure using X-ray diffraction (XRD). The surface morphology and thickness of BST the films were characterized by atomic force microscopy (AFM) and field emission scanning electron microscope (FESEM). We measured the dielectric properties at microwave frequencies (1~3 GHz) using a symmetrical stripline resonator with shorted ends and terahertz frequencies (0.2~2.5 THz) using a time-domain terahertz spectroscopy. The real and imaginary parts of the complex dielectric constant of the BST thin films on LAO substrates were in agreement with those previously reported.

• Current Optics and Photonics
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• 제6권6호
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• pp.619-626
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• 2022

In this study, we develop a three-dimensional (3D) terahertz time-of-flight (THz-TOF) imaging technique with a large depth range, based on asynchronous optical sampling (ASOPS) methods. THz-TOF imaging with the ASOPS technique enables rapid scanning with a time-delay span of 10 ns. This means that a depth range of 1.5 m is possible in principle, whereas in practice it is limited by the focus depth determined by the optical geometry, such as the focal length of the scan lens. We characterize the spatial resolution of objects at different vertical positions with a focal length of 5 cm. The lateral resolution varies from 0.8-1.8 mm within the vertical range of 50 mm. We obtain THz-TOF images for samples with multiple reflection layers; the horizontal and vertical locations of the objects are successfully determined from the 2D cross-sectional images, or from reconstructed 3D images. For instance, we can identify metallic objects embedded in insulating enclosures having a vertical depth range greater than 30 mm. For feasible practical use, we employ the proposed technique to locate a metallic object within a thick chocolate bar, which is not accessible via conventional transmission geometry.