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ABSTRACT: In a strongly scattering medium where Anderson localization takes place, constructive interference of local non-propagating waves dominate over the incoherent addition of propagating waves. This results in the disappearance of propagating waves within the medium, which significantly attenuates energy transmission. In this numerical study performed in the optical regime, we systematically found resonance modes, called eigenchannels, of a 2-D Anderson localized system that allow for the near-perfect energy transmission. We observed that the internal field distribution of these eigenchannels exhibit dense clustering of localized modes. This strongly suggests that the clustered resonance modes facilitate long-range energy flow of local waves. Our study explicitly elucidates the interplay between wave localization and transmission enhancement in the Anderson localization regime.
Optics Express 08/2012; 20(18):20721-9. · 3.59 Impact Factor
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ABSTRACT: Optical antennas interface an object with optical radiation and boost the absorption and emission of light by the objects through the antenna modes. It has been much desired to enhance both excitation and emission processes of the quantum emitters as well as to interface multiwavelength channels for many nano-optical applications. Here we report the experimental implementation of an optical antenna operating in the full visible range via surface plasmon currents induced in a defect-free single-crystalline Ag nanowire (NW). With its atomically flat surface, the long Ag NW reliably establishes multiple plasmonic resonances and produces a unique rainbow antenna radiation in the Fresnel region. Detailed antenna radiation properties, such as radiating near-field patterns and polarization states, were experimentally examined and precisely analyzed by numerical simulations and antenna theory. The multiresonant Ag NW nanoantenna will find superb applications in nano-optical spectroscopy, high-resolution nanoimaging, photovoltaics, and nonlinear signal conversion.
Nano Letters 04/2012; 12(5):2331-6. · 13.20 Impact Factor
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ABSTRACT: We numerically observe that open eigenmodes enhance the energy stored inside disordered media and prove that eigenmodes contribute to a single-channel optimizing mode, which is realized in recent experiments, in proportion to their eigenvalues.
Lasers and Electro-Optics (CLEO), 2011 Conference on; 06/2011
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ABSTRACT: The rhombic dodecahedral Au nanocrystals enclosed by 12 {110} facets could be readily prepared without the use of any seeds, surfactants, or foreign metal ions but only with N,N-dimethylformamide as both reductant and solvent.
Journal of the American Chemical Society 02/2009; 131(5):1672-3. · 9.91 Impact Factor
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Taejoon Kang,
Ilsun Yoon,
Ki-Seok Jeon,
Wonjun Choi,
Yonghun Lee,
Kwanyong Seo,
Youngdong Yoo, Q-Han Park,
Hyotcherl Ihee,
Yung Doug Suh,
Bongsoo Kim
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ABSTRACT: Well-defined surface-enhanced Raman scattering (SERS) active systems were fabricated by single-crystalline noble metal nanowires. Crossed and parallel nanowire pairs were constructed by using a nanomanipulator to create SERS hot spots in the form of nanowire junction. SERS spectra of brilliant cresyl blue (BCB), p-mercaptoaniline (pMA), and p-mercaptobenzoic acid (pMBA) were observed at the junction of two nanowires. The SERS enhancement and polarization dependence are correlated well with the enhanced electric field intensities calculated by the finite difference time domain (FDTD) method for specific nanowire geometries. These simple and effective SERS active systems have a practical advantage that the hot spots can be readily located and visualized by an optical microscope. These well-defined SERS active systems based on noble metal nanowires can be further developed to find applications in a variety of biological and chemical sensing.
The Journal of Physical Chemistry C 01/2009; 113:7492. · 4.80 Impact Factor
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ABSTRACT: Fabricating well-defined and highly reproducible platforms for surface-enhanced Raman scattering (SERS) is very important in developing practical SERS sensors. We report a novel SERS platform composed of a single metallic nanowire (NW) on a metallic film. Optical excitation of this novel sandwich nanostructure provides a line of SERS hot spots (a SERS hot line) at the gap between the NW and the film. This single nanowire on a film (SNOF) architecture can be easily fabricated, and the position of hot spots can be conveniently located in situ by using an optical microscope during the SERS measurement. We show that high-quality SERS spectra from benzenethiol, brilliant cresyl blue, and single-stranded DNA can be obtained on a SNOF with reliable reproducibility, good time stability, and excellent sensitivity, and thus, SNOFs can potentially be employed as effective SERS sensors for label-free biomolecule detection. We also report detailed studies of polarization- and material-dependent SERS enhancement of the SNOF structure.
Journal of the American Chemical Society 01/2009; 131(2):758-62. · 9.91 Impact Factor
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Paritosh Mohanty,
Ilsun Yoon,
Taejoon Kang,
Kwanyong Seo,
Kumar S K Varadwaj,
Wonjun Choi, Q-Han Park,
Jae Pyung Ahn,
Yung Doug Suh,
Hyotcherl Ihee,
Bongsoo Kim
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ABSTRACT: We report vapor-phase synthesis of single-crystalline free-standing Ag nanowires and polarized surface-enhanced Raman scattering (SERS) of a single nanowire, as a first step toward fabrication of well-controlled nanobiosensors employing the SERS technique.
Journal of the American Chemical Society 09/2007; 129(31):9576-7. · 9.91 Impact Factor
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ABSTRACT: While the distribution of the transmission eigenvalues of a disordered medium is well understood in the context of random-matrix theory, the properties of eigenchannels have remained unexplored. In this study, we have solved electromagnetic wave propagation through a disordered medium using the finite-difference time-domain method, we numerically constructed a transmission matrix in an optical regime, and we obtained its eigenchannels as well as its eigenvalues. We observe that open eigenchannels enhance the energy stored inside the disordered medium. From mode decomposition, we prove that eigenchannels contribute to a single-channel optimizing mode, which is realized in recent experiments by I. M. Vellekoop et al. Phys. Rev. Lett 101 120601 (2008)], in proportion to their eigenvalues. Our study will pave the way for experimental approaches to finding open eigenchannels and their potential use for imaging through turbid media and random lasers.
Phys. Rev. B. 83(13).
