• Journal of the Optical Society of Korea
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• 제20권2호
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• pp.263-268
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• 2016

Broadband metal-dielectric-metal terahertz filters composed of complementary rings are designed and demonstrated. Four samples with different parameters were fabricated. Results measured using THz time-domain spectroscopy system show excellent agreement with simulations. Compared with the broadband filters reported before, the complementary ring structure in our design is insensitive to any polarization at normal incidence due to symmetry of the ring. Furthermore, the influence of structure parameters (such as period, radius, slot width, thickness and incidence angles) on the transmission characteristics has been investigated theoretically. The encouraging results afforded by designing of the filters could find applications in broadband sensors, terahertz communication systems, and other emerging terahertz technologies.

• 한국생산제조학회지
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• 제21권6호
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• pp.1003-1007
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• 2012

A nondestructive technique would be very useful. Advanced NDE T-ray (terahertz ray) techniques of technology and instrumentation has provided a probing field on the electromagnetic spectrum. However, the T-ray is limited in order to penetrate a conducting material to some degree. Here, the T-ray would not go through easily the CFRP composite laminates since carbon fibers are electrically conducting while the epoxy matrix is not. So, investigation of terahertz time domain spectroscopy (THz TDS) was made and reflection and transmission configurations were studied for a 48-ply thermoplastic PPS(poly-phenylene sulfide)-based CFRP solid laminate. It is found that the electrical conductivity of CFRP composites depends on the direction of unidirectional fibers.

• 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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• 제5권4호
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• pp.370-374
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• 2021

Corals are the remains of animals that grow on warm beaches. They have been used as decorative jewels because of their variety of colors, and as medicinal materials for treating cancers, AIDS, and other therapeutic uses because of their chemical elements. Corals are mainly composed of calcium carbonate (CaCO₃) and have many air pores, tens to hundreds of micrometers in size. The refractive indices and absorption coefficients of dried sliced staghorn corals are investigated using terahertz time-domain spectroscopy. The measured values are similar to those for CaCO₃, as expected. It is observed that a sample with a microstructure formed by air pores can guide terahertz waves. The dispersion, effective index, and loss of the guiding modes of coral core surrounded by five triangular air pores are numerically calculated. The simulated spatial distribution of the electric field of the guide mode at 1.25 THz shows the mode to be tightly confined to the core.

• 한국광학회지
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• 제19권6호
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• pp.435-438
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• 2008

중수($D_2O$, 산화중수소)는 수소원자(H)보다 중성자 한 개가 더 많은 수소원자 동위원소(D)로 이루어진 물이다. 중수는 자연 상태의 물 가운데 5만분의 1정도 존재하며 경수($H_2O$)와 매우 비슷한 성질을 가지고 있으나 경수보다 11%정도 무겁고, 특이점은 235 K로 228 K인 경수와 약간의 차이를 가진다. 중수는 중성자를 흡수하여 원자로의 중성자 감속재로 쓰이고 최근 중수 농도에 따라 세포에 미치는 독성효과가 다르게 나타나는 현상이 발견 되어 암 치료에 사용하려는 연구가 진행되고 있다. 우리는 테라헤르츠 시간축 분광학을 이용하여 경수와 중수 혼합물의 농도별 굴절률과 흡수율 변화를 거대 분자간 결합에너지 영역을 포함하는 테라헤르츠 영역 ($0{\sim}2.5\;THz$)에서 측정하여 중수의 비율이 높을수록 굴절률은 감소하고 흡수율 또한 감소하는 결과를 얻었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.139.2-139.2
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• 2016

Electrons and phonons in chalcogenide-based materials play are important factors in the performance of an optical data storage media and thermoelectric devices. However, the fundamental kinetics of carriers in chalcogenide materials remains controversial, and active debate continues over the mechanism responsible for carrier relaxation. In this study, we investigated ultrafast carrier dynamics in an multilayered $\{Sb(3{\AA})/Te(9{\AA})\}n$ thin film during the transition from the amorphous to the crystalline phase using optical pump terahertz probe spectroscopy (OPTP), which permits the relationship between structural phase transition and optical property transitions to be examined. Using THz-TDS, we demonstrated that optical conductance and carrier concentration change as a function of annealing temperature with a contact-free optical technique. Moreover, we observed that the topological surface state (TSS) affects the degree of enhancement of carrier lifetime, which is closely related to the degree of spin-orbit coupling (SOC). The combination of an optical technique and a proposed carrier relaxation mechanism provides a powerful tool for monitoring TSS and SOC. Consequently, the response of the amorphous phase is dominated by an electron-phonon coupling effect, while that of the crystalline structure is controlled by a Dirac surface state and SOC effects. These results are important for understanding the fundamental physics of phase change materials and for optimizing and designing materials with better performance in optoelectronic devices.