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Colossal Absorption of Molecules Inside Single Terahertz Nanoantennas
Park, Hyeong-Ryeol,Ahn, Kwang Jun,Han, Sanghoon,Bahk, Young-Mi,Park, Namkyoo,Kim, Dai-Sik American Chemical Society 2013 Nano letters Vol.13 No.4
<P>Molecules have extremely small absorption cross sections in the terahertz range even under resonant conditions, which severely limit their detectability, often requiring tens of milligrams. We demonstrate that nanoantennas tailored for the terahertz range resolves the small molecular cross section problem. The extremely asymmetric electromagnetic environment inside the slot antenna, which finds the electric field being enhanced by thousand times with the magnetic field changed little, forces the molecular cross section to be enhanced by >10<SUP>3</SUP> accompanied by a colossal absorption coefficient of ∼170 000 cm<SUP>–1</SUP>. Tens of nanograms of small molecules such as 1,3,5-trinitroperhydro-1,3,5-triazine (RDX) and lactose drop-cast over an area of 10 mm<SUP>2</SUP>, with only tens of femtograms of molecules inside the single nanoslot, can readily be detected. Our work enables terahertz sensing of chemical and biological molecules in ultrasmall quantities.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2013/nalefd.2013.13.issue-4/nl400374z/production/images/medium/nl-2013-00374z_0001.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl400374z'>ACS Electronic Supporting Info</A></P>
Raman-based distributed temperature sensor with simplex coding and link optimization
Jonghan Park,Bolognini, G.,Duckey Lee,Pilhan Kim,Pilki Cho,Di Pasquale, F.,Namkyoo Park IEEE 2006 IEEE photonics technology letters Vol.18 No.17
<P>In this letter, a coded, Raman-based distributed temperature sensor system using 255-bit Simplex coded optical time domain reflectometry (OTDR) and optimized sensing link composed of cascaded fibers with different Raman coefficients, is proposed. This system is compared to a system with an uncoded OTDR on standard single-mode fiber, demonstrating significant enhancement in the interrogation distance (19.5 km from coding gain, and 9.6 km from link optimization). Total sensing range of 37 km at 17-m/3-K spatial/temperature resolution were achieved, while employing conventional low power (80 mW) laser diodes</P>
Active Terahertz Nanoantennas Based on VO<sub>2</sub> Phase Transition
Seo, Minah,Kyoung, Jisoo,Park, Hyeongryeol,Koo, Sukmo,Kim, Hyun-sun,Bernien, Hannes,Kim, Bong Jun,Choe, Jong Ho,Ahn, Yeong Hwan,Kim, Hyun-Tak,Park, Namkyoo,Park, Q-Han,Ahn, Kwangjun,Kim, Dai-sik American Chemical Society 2010 Nano letters Vol.10 No.6
<P>Unusual performances of metamaterials such as negative index of refraction, memory effect, and cloaking originate from the resonance features of the <I>metallic composite atom</I><SUP>1−6</SUP>. Indeed, control of metamaterial properties by changing dielectric environments of thin films below the metallic resonators has been demonstrated<SUP>7−11</SUP>. However, the dynamic control ranges are still limited to less than a factor of 10,<SUP>7−11</SUP> with the applicable bandwidth defined by the sharp resonance features. Here, we present ultra-broad-band metamaterial thin film with colossal dynamic control range, fulfilling present day research demands. Hybridized with thin VO<SUB>2</SUB> (vanadium dioxide)(12-18) films, nanoresonator supercell arrays designed for one decade of spectral width in terahertz frequency region show an unprecedented extinction ratio of over 10000 when the underlying thin film experiences a phase transition. Our nanoresonator approach realizes the full potential of the thin film technology for long wavelength applications.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2010/nalefd.2010.10.issue-6/nl1002153/production/images/medium/nl-2010-002153_0002.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl1002153'>ACS Electronic Supporting Info</A></P>
Giant nonlinear response of terahertz nanoresonators on VO_2 thin film
Kyoung, Jisoo,Seo, Minah,Park, Hyeongryeol,Koo, Sukmo,Kim, Hyun-sun,Park, Youngmi,Kim, Bong-Jun,Ahn, Kwangjun,Park, Namkyoo,Kim, Hyun-Tak,Kim, Dai-Sik The Optical Society 2010 Optics express Vol.18 No.16
<P>We report on an order of magnitude enhanced nonlinear response of vanadium dioxide thin film patterned with nanoresonators - nano slot antennas fabricated on the gold film. Transmission of terahertz radiation, little affected by an optical pumping for the case of bulk thin film, can now be completely switched-off: DeltaT/T approximately -0.9999 by the same optical pumping power. This unprecedentedly large optical pump-terahertz probe nonlinearity originates from the insulator-to-metal phase transition drastically reducing the antenna cross sections of the nanoresonators. Our scheme enables nanoscale-thin film technology to be used for all-optical switching of long wavelength light.</P>
Superresolution Digital Image Enhancement by Subpixel Image Translation With a Scanning Micromirror
Yu, Kyoungsik,Park, Namkyoo,Lee, Daesung,Solgaard, Olav IEEE 2007 IEEE journal on selected topics in quantum electro Vol.13 No.2
<P>This paper reports on a superresolution digital image enhancement technique using subpixel image translation with a scanning micromirror. We demonstrate that the spatial resolution of digital photomicrography, employing typical black-and-white pixelated image sensors, can be improved by acquiring multiple images with predetermined subpixel shifts and combining them with a superresolution image reconstruction algorithm. A two-axis gimbaled micromirror fabricated with a bulk-micromachining process is used to control the translational image displacements with subpixel accuracy</P>
Oh, Yongtaek,Park, Sung Won,Chun, Sung-Min,Lim, Namkyoo,Ahn, Ki Sup,Ka, Jong-Ok,Jin, Dong-Kyu,Han, Byoung-Don Adis International 2009 Molecular diagnosis & therapy Vol.13 No.6
<P>Congenital adrenal hyperplasia (CAH) is an autosomal recessive disease caused by mutations in the CYP21A2 gene, which codes for steroid 21-hydroxylase. More than 90% of patients with CAH have mutations in CYP21A2 or have large deletions in the RCCX module on chromosome 6p21.3, which also includes the pseudogene CYP21A1P. Genotyping of CYP21A2 is required for diagnosis of CAH, but current genotyping methods, such as direct sequencing, allele-specific PCR amplification, or PCR amplification and restriction fragment length polymorphism (PCR-RFLP) still need further improvements to reduce test time and cost.</P>
Design of all-optical read-only memory
Jung, Young Jin,Park, Namkyoo,Jhon, Young Min,Lee, Seok The Optical Society 2009 Applied Optics Vol.48 No.31
<P>A semiconductor optical amplifier-based all-optical read-only memory (ROM) is successfully demonstrated through simulations using a one-level simplification method optimized for optical logic circuits. Design details are presented, and advantages are discussed in comparison with an all-optical ROM-employing decoder. We demonstrate that eight characters can be stored at each address in the American Standard Code for Information Interchange.</P>