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ABSTRACT: Nature-inspired devices and architectures are attracting considerable attention for various purposes, including developing novel computing based on spatiotemporal dynamics, exploiting stochastic processes for computing, and reducing energy dissipation. This paper demonstrates that the optical energy transfer between quantum nanostructures mediated by optical near-field interactions occurring at scales far below the wavelength of light could be utilized for solving constraint satisfaction problems (CSPs). The optical energy transfer from smaller quantum dots to larger ones, which is a quantum stochastic process, depends on the existence of resonant energy levels between the quantum dots or a state-filling effect occurring at the larger quantum dots. Such a spatiotemporal mechanism yields different evolutions of energy transfer patterns in multi-quantum-dot systems. We numerically demonstrate that optical energy transfer processes can be used to solve a CSP. The work described in this paper is a first step in showing the applicability and potential of nanometer-scale optical near-field processes toward solving computationally demanding problems.
Physical Review B 09/2012; 86:125407. · 3.69 Impact Factor
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ABSTRACT: Recently, light-assisted nanofabrication have been introduced, such as the
synthesis of quantum dots using photo-induced desorption that yields reduced
size fluctuations, or metal sputtering under light illumination resulting in
self-organized, nanoparticle chains. The physical mechanisms have originally
been attributed to material desorption or plasmon resonance effects. However,
significant stochastic phenomena are also present that have not been explained
yet. We introduce stochastic models taking account of the light-assisted
processes that reproduce phenomenological characteristics consistent with the
experimental observations.
04/2012;
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ABSTRACT: We demonstrate optical excitation transfer in a mixture composed of quantum dots of two different sizes (larger and smaller) networked via optical near-field interactions. For the optical near-field interaction network based on a density matrix formalism, we introduce an optimal mixture that agrees with experimental results. Based on these findings, we theoretically examine the topology-dependent efficiency of optical excitation transfer, which clearly exhibits autonomous, energy-efficient networking behavior occurring at the nanometer scale. We discuss what we can learn from this optical excitation transfer and its implications for information and communications applications.
Nano Communication Networks 12/2011; 2(4):189-195.
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ABSTRACT: We experimentally demonstrated the basic concept of modulatable optical near-field interactions by utilizing energy transfer between closely positioned resonant CdSe/ZnS quantum dot (QD) pairs dispersed on a flexible substrate. Modulation by physical flexion of the substrate changes the distances between quantum dots to control the magnitude of the coupling strength. The modulation capability was qualitatively confirmed as a change of the emission spectrum. We defined two kinds of modulatability for quantitative evaluation of the capability, and an evident difference was revealed between resonant and non-resonant QDs.
Optics Express 09/2011; 19(19):18260-71. · 3.59 Impact Factor
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ABSTRACT: Exploiting the unique attributes of nanometer-scale optical near-field interactions in a completely parallel manner is important
for innovative nanometric optical processing systems. In this paper, we propose the basic concepts necessary for parallel
retrieval of light–matter interactions on the nanometer-scale instead of the conventional one-dimensional scanning method.
One is the macro-scale observation of optical near-fields, and the other is the transcription of optical near-fields. The former converts effects occurring locally on the nanometer scale involving optical near-field
interactions to propagating light radiation, and the latter magnifies the distributions of optical near-fields from the nanometer
scale to the sub-micrometer one. Those techniques allow us to observe optical far-field signals that originate from the effects
occurring at the nanometer scale. We numerically verified the concepts and principles using electromagnetic simulations.
12/2009: pages 298-307;
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ABSTRACT: Nanophotonics has the potential to provide novel devices and systems with unique functions based on optical near-field interactions. Here we experimentally demonstrate, for the first time, what we call a quadrupole-dipole transform achieved by optical near-field interactions between engineered nanostructures. We describe its principles, the nanostructure design, fabrication of one- and two-layer gold nanostructures, an experimental demonstration, and optical characterization and analysis.
Optics Express 07/2009; 17(13):11113-21. · 3.59 Impact Factor
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ABSTRACT: Nonadiabatic optical near-field etching is a novel way of polishing surfaces of optical elements without any mechanical contact processes. It selectively induces photochemical reactions on the surface in regions where optical near fields are excited, namely, in the vicinity of portions having fine-scale rough structures, which leads to reduced surface roughness. In this paper, we analyze the surface roughness of optical elements planarized by nonadiabatic optical near-field etching based on power spectrum-based methods. Our analysis clearly reveals the effects of the near-field etching which are otherwise concealed when using conventional roughness measures such as the roughness average (R<sub>a</sub>) . We also investigate the effect of planarization via numerical simulations using surface profiles obtained experimentally before and after the near-field etching.
Journal of Applied Physics 04/2009; · 2.17 Impact Factor
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ABSTRACT: A "hierarchical hologram" and experiments using it are described. This type of hologram works both in optical far-fields and near-fields.We exploit the physical difference between the propagating light and optical near-field, where the former is associated with conventional holographic patterns obtained in optical far-fields, whereas the latter is associated with nanometric structure accessible only via optical near-fields. We also describe an experimental demonstration of the basic principles with our prototype optical elements.
Optics Express 02/2008; 16(2):607-12. · 3.59 Impact Factor
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ABSTRACT: We report the self-assembly of a size- and position-controlled ultralong nanodot chain using a novel effect of near-field optical desorption. A sub-100-nm dot chain with a deviation of 5 nm forms at a size based on plasmon resonance, depending on the photon energy; the resulting structure forms a high-transmission-efficiency nanoscale waveguide. Using this method with simple lithographically patterned substrates allows one to increase the throughput of the production of nanoscale structures dramatically at all scales.
Nano Letters 01/2006; 5(12):2548-51. · 13.20 Impact Factor
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ABSTRACT: Optical near-field interactions exhibit different behavior at different scales, which we term scale-dependent physical hierarchy. Using the intrinsic logical hierarchy of information and a simple digital coding scheme, scale-dependent optical memory accesses are associated with different levels of the information hierarchy. The basic principle is demonstrated by finite-different time-domain simulations and experiments using metal nanoparticles.
Optics Express 12/2005; 13(23):9265-71. · 3.59 Impact Factor
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ABSTRACT: In the first half of this chapter, a novel fabrication method called nanophotonic polishing is reviewed. This method is a
probeless and maskless optical processing technique that employs a nonadiabatic photochemical reaction
. Nanophotonics has already brought about innovation in fabrication methods, such as with photochemical vapor deposition [1]
and photolithography [2]. Conventional photochemical vapor deposition is a way to deposit materials on a substrate using a
photochemical reaction with ultraviolet light that predissociates metal-organic molecules by irradiating gaseous molecules
or molecules adsorbed on the substrate.
01/1970: pages 113-130;
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ABSTRACT: We theoretically and experimentally investigated a system composed of a mixture of different-sized quantum dots involving optical near-field interactions to effectively induce optical excitation transfer. We demonstrated that the ratio of the number of smaller quantum dots to larger ones can be optimized using a density-matrix formalism so that excitons generated in the smaller ones are efficiently transferred to the larger ones. We also describe experimental demonstrations based on a mixture of 2 nm- and 2.8 nm-diameter CdSe/ZnS quantum dots dispersed on the surface of a silicon photodiode, where the increase in induced photocurrents due to optical excitation transfer is maximized at a certain quantum dot mixture which agrees with theoretical calculations.
Phys. Rev. B. 80(12).
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ABSTRACT: Particles several tens of nanometers in size were aligned in the desired positions in a controlled manner by using capillary force interaction and suspension flow. Latex beads 40-nm in diameter were aligned linearly around a 10-μm-hole template fabricated by lithography. Further control of their position and separation was realized using colloidal gold nanoparticles by controlling the particle-substrate and particle-particle interactions using an optical near field generated on the edge of a Si wedge, in which the separation of the colloidal gold nanoparticles was controlled by the direction of polarization.
