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Terahertz substance imaging by waveform shaping.
Yi, Minwoo,Kim, Hyosub,Jin, Kyong Hwan,Ye, Jong Chul,Ahn, Jaewook Optical Society of America 2012 Optics express Vol.20 No.18
<P>Terahertz pulse shaping technique is used to adaptively design terahertz waveforms of enhanced spectral correlation to particular materials among a given set of materials. In a proof-of-principle experiment performed with a two-dimensional image target consisted of meta-materials of distinctive resonance frequencies, the as-designed waveforms are used to demonstrate terahertz substance imaging. It is hoped that this material-specific terahertz waveforms may enable single- or few-shot terahertz material classification when being used in conjunction with terahertz power measurement.</P>
Optimal Molar Fractions of Ternary Zinc-Blende Terahertz Emitters
Minwoo Yi,안재욱,Kanghee Lee 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.51 No.2I
We report our calculation of optimal molar fractions in various ternary zinc-blende terahertz emitters that can produce terahertz radiation with enhanced powers when the wavelength of the pump laser is changed. While the momentum mismatch between the optical and the terahertz pulses in these non-resonant nonlinear materials was mainly used to understand the spectral and the transient shapes of the generated terahertz waves, the optimal molar fractions in compound semiconductor terahertz emitters were better determined with the full numerical calculations. To demonstrate the output power change and the sensitivity of the calculation, we performed numerical simulations of the optical rectification process during the optical and the terahertz wave propagations. The result suggests that the optimal Cd compositions in Zn$_{1-x}$Cd$_{x}$Te are $x=0.10$ at $\lambda=820$ nm and $x=0.65$ at $\lambda=850$ nm and that the Te compositions in ZnSe$_{1-x}$Te$_{x}$ are $x=0.6$ at $\lambda=750$ nm and $x=0.95$ at $\lambda=820$ nm. This method could act as a powerful tool to optimally design various zinc-blende semiconductor compounds to generate terahertz waveforms
Terahertz waves emitted from an optical fiber
Yi, Minwoo,Lee, Kanghee,Lim, Jongseok,Hong, Youngbin,Jho, Young-Dahl,Ahn, Jaewook The Optical Society 2010 Optics express Vol.18 No.13
<P>We report a simple method of creating terahertz waves by applying the photo-Dember effect in a (100)-oriented InAs film coated onto the 45-degree wedged-end facet of an optical fiber. The terahertz waves are generated by infrared pulses guided through the optical fiber which is nearly in contact with a sample and then measured by a conventional photo-conductive antenna detector. Using this alignment-free terahertz source, we performed proof-of-principle experiments of terahertz time-domain spectroscopy and near-field terahertz microscopy. We obtained a bandwidth of 2 THz and 180-microm spatial resolution. Using this method, the THz imaging resolution is expected to be reduced to the size of the optical fiber core. Applications of this device can be extended to sub-wavelength terahertz spectroscopic imaging, miniaturized terahertz system design, and remote sensing.</P>
이민우(Minwoo Yi),양종원(Jongwon Yang),이우상(Woosang Lee),장원(Won Jang),소준호(Joonho So) 한국전자파학회 2016 한국전자파학회논문지 Vol.27 No.4
밀리미터파 대역인 W-대역에서 초고이득 반사배열안테나를 구현하기 위하여 이중 반사판형태 중 주 반사판으로 향하는 전파가 급전부로 되돌아오지 않도록 하여 안테나의 효율 및 이득 특성을 크게 개선한 축이동 그레고리안 안테나를 금속 반사배열안테나 형태로 구현하였다. 금속 반사배열안테나의 경우, 유전체를 이용한 반사배열의 안테나와 달리 기판에 의한 손실이 없으며, 금속가공만으로 제작될 수 있는 제작의 편의성을 갖고 있다. 본 논문에서는 사각형 금속 개구의 배열을 이용하여 50 ㏈i 이상의 초고이득 축이동 금속 반사배열안테나를 설계하고, 일반적인 기계 가공을 이용하여 안테나를 제작하였으며, 제작된 안테나는 밀리미터파 컴팩트 레인지 안테나 측정시스템을 이용하여 검증하였다. We design a displaced-axis Gregorian dual antenna in the form of a metal reflectarray antenna for millimeter wave region, W-band. Unlike a reflectarray composed of printed patch antennas on a dielectric substrate, metallic rectangular waveguide unit-cells are proposed to avoid the loss of substrate and take an advantage of ease of typical metal machining fabrication. In this paper, the radiation characteristics of constructed metal reflectarray antennas show ultra high-gain antenna over 50 ㏈i at a target frequency in W-band. The experimental measurements are conducted in millimeter-wave compact range antenna measurement system.
Antifungal Activity of Streptomyces sp. Against Puccinia recondite Causing Wheat Leaf Rust
YI, YONGSUB,KIM, SEUNGHYUN,KIM, MINWOO,CHOI, GYUNG JA,CHO, KWANG YUN,SONG, JAEKYEONG,LIM, YOONGHO 한국미생물 · 생명공학회 2004 Journal of microbiology and biotechnology Vol.14 No.2
To discover a potent strain against wheat leaf rust, soil samples collected from Ilgamho, Seoul, Korea were tested in vivo and a strain belonging to Streptomyces sp. was found to show good antifungal activity when fermented in a broth. The identification of the strain was carried out based on 16s rDNA analysis, and the active compound was separated from the fermented broth. Even though its structure was not determined completely, the authors report the results obtained so far indicate that the fermented broth of the strain showed activity against wheat leaf rust. Therefore, we propose that this may be a potential novel strain showing antifangal activity against Puccinia reconditu.