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Selective enhanced resonances of two asymmetric terahertz nano resonators.
Bahk, Young-Mi,Choi, Jae-Wook,Kyoung, Jisoo,Park, Hyeong-Ryeol,Ahn, Kwang Jun,Kim, Dai-Sik Optical Society of America 2012 Optics express Vol.20 No.23
<P>We studied the electromagnetic interaction between two asymmetric terahertz nano resonators, rectangular holes which have a few hundred micron lengths but nanoscale widths. We report that the dominant resonant transmission of the structures can be modulated by the horizontal distance between two rectangles due to the different oscillation strength of the asymmetric coupling at two different resonance frequencies. Our results are significant for an optimum design of rectangular holes in terahertz frequency regime for applications such as sensitive nanoparticle detection and terahertz filters.</P>
Plasmon Enhanced Terahertz Emission from Single Layer Graphene
Bahk, Young-Mi,Ramakrishnan, Gopakumar,Choi, Jongho,Song, Hyelynn,Choi, Geunchang,Kim, Yong Hyup,Ahn, Kwang Jun,Kim, Dai-Sik,Planken, Paul C. M. American Chemical Society 2014 ACS NANO Vol.8 No.9
<P>We show that surface plasmons, excited with femtosecond laser pulses on continuous or discontinuous gold substrates, strongly enhance the generation and emission of ultrashort, broadband terahertz pulses from single layer graphene. Without surface plasmon excitation, for graphene on glass, ‘<I>nonresonant laser-pulse-induced photon drag currents</I>’ appear to be responsible for the relatively weak emission of both <I>s</I>- and <I>p</I>-polarized terahertz pulses. For graphene on a discontinuous layer of gold, only the emission of the <I>p</I>-polarized terahertz electric field is enhanced, whereas the <I>s</I>-polarized component remains largely unaffected, suggesting the presence of an additional terahertz generation mechanism. We argue that in the latter case, ‘<I>surface-plasmon-enhanced optical rectification</I>’, made possible by the lack of inversion symmetry at the graphene on gold surface, is responsible for the strongly enhanced emission. The enhancement occurs because the electric field of surface plasmons is localized and enhanced where the graphene is located: at the surface of the metal. We believe that our results point the way to small, thin, and more efficient terahertz photonic devices.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2014/ancac3.2014.8.issue-9/nn5025237/production/images/medium/nn-2014-025237_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn5025237'>ACS Electronic Supporting Info</A></P>
Ultimate terahertz field enhancement of single nanoslits
Bahk, Young-Mi,Han, Sanghoon,Rhie, Jiyeah,Park, Joohyun,Jeon, Hyeongtag,Park, Namkyoo,Kim, Dai-Sik American Physical Society 2017 Physical Review B Vol.95 No.7
<P>A single metallic slit is the simplest plasmonic structure for basic physical understanding of electromagnetic field confinement. By reducing the gap size, the field enhancement is expected to first go up and then go down when the gap width becomes subnanometer because of the quantum tunneling effects. A fundamental question is whether we reach the classical limit of field enhancement before entering the quantum regime, i.e., whether the quantum effects undercut the highest field enhancement classically possible. Here, by performing terahertz time domain spectroscopy on single slits of widths varying from 1.5 nm to 50 mu m, we show that ultimate field enhancement determined by the wavelength of light and film thickness can be reached before we hit the quantum regime. Our paper paves way toward designing a quantum plasmonic system with maximum control yet without sacrificing the classical field enhancements.</P>
DEVELOPMENTALLY REGULATED EXPRESSION OF THE RICE CALMODULIN PROMOTER IN TRANSGENIC TOBACCO PLANTS
Choi, Young-Ju,Lim, Chae-Oh,Koo, Ja-Choon,Lee, Sang-Hyeung,Kang, Mi-Sun,Bahk, Jeong-Dong,Cho, Moo-Je Gyeongsang National University Chinju, Korea 1992 Plant molecular biology and biotechnology research Vol.1992 No.
Kang, Young-Min,Lee, Ok-Sun,Jung, Hee-Young,Kang, Seung-Mi,Lee, Byung-Hyun,Chandrakant Karigar,Theertha Prasad,Bahk, Jung-Dong,Choi, Myung-Suk Plant molecular biology and biotechnology research 2005 Plant molecular biology and biotechnology research Vol.2005 No.
The hyoscyamine 6β-hydroxylase (h6h) gene was introduced into the genome of Scopolia parviflora through the Agrobacterium rhizogenes binary vector system. The enzyme was expressed ally and tissue specific selectively in roots, resulting in five transgenic hairy root lines. The presence of the h6h gene in kanamycin-resistant hairy roots and its overexpression were confirmed by polymerase chain reaction (PCR), Northern blotting, and Western blotting, respectively. In the transgenic hairy root lines which constitutively expressed the H6H enzyme, hyoscyamine and scopolamine accumulated in high concentration. Among the transgenic hairy root lines that expressed the H6H enzyme, only two were more productive. The levels of tropane alkaloids in transgenic hairy root varied greatly: The best transgenic line (#5) contained 8.12 mg of scopolamine per g dry weight, which produced the compoung three times more than wild-type root. These results suggest a possibility of improving the yield of tropane alkaloids in hairy root lines by genetic and metabolic engineering.