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Novitsky A.,Technical University of Denmark | Qiu C.-W.,National University of Singapore | Wang H.,Data Storage Institute Singapore
Physical Review Letters | Year: 2011

Usually a light beam pushes a particle when the photons act upon it. We investigate the optical forces by nonparaxial gradientless beams and find that the forces can drag suitable particles all the way towards the light source. The major criterion of realizing the backward dragging force is the strong nonparaxiality of the light beam, which contributes to the pulling force owing to momentum conservation. The nonparaxiality of the Bessel beam can be manipulated to possess a dragging force along both the radial longitudinal directions, i.e., a "tractor beam" with stable trajectories is achieved. © 2011 American Physical Society.

Rahmani M.,Data Storage Institute Singapore | Rahmani M.,National University of Singapore | Luk'yanchuk B.,Data Storage Institute Singapore | Hong M.,National University of Singapore
Laser and Photonics Reviews | Year: 2013

Recently, a large number of experimental and theoretical works have revealed a variety of plasmonic nanostructures with the capabilities of Fano resonance (FR) generation. Among these structures, plasmonic oligomers consisting of packed metallic nanoelements with certain configurations have been of significant interest. Oligomers can exhibit FR independently of the polarization direction based on dipole-dipole antiparallel modes without the need to excite challenging high-order modes. The purpose of this review article is to provide an overview of recent achievements on FR of plasmonic nanostructures in recent years. Meanwhile, more attention is given to the optical properties of plasmonic oligomers due to the high potential of such structures in optical spectra engineering. © 2012 by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ding W.,National University of Singapore | Luk'Yanchuk B.,Data Storage Institute Singapore | Qiu C.-W.,National University of Singapore
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2012

We report a distinguished mechanism of using two interaction-free (uncoupled) cavities to realize an all-optical silicon diode with an extremely high contrast ratio. In contrast to existing examples of all-optical diodes, our unidirectional transmission results from mimicking Fano resonance in a compact and finite silicon waveguide. A Fano spectrum with an arbitrary asymmetric factor, resonant center, and linewidth is explicitly designed with two symmetric resonances, which can be separately realized and tuned in an insightful manner by two cascaded uncoupled cavities. The field localizations are inherently asymmetric. We show that if these double asymmetries (Fano spectrum and field localization) are integrated and controlled, an ultrahigh-contrast-ratio silicon Fano diode is accomplished. This finding provides a promising avenue for achieving an extremely compact optical switch and incorporating Fano resonance in silicon photonics. © 2012 American Physical Society.

Luk'Yanchuk B.,Data Storage Institute Singapore | Zheludev N.I.,University of Southampton | Maier S.A.,Imperial College London | Halas N.J.,Rice University | And 4 more authors.
Nature Materials | Year: 2010

Since its discovery, the asymmetric Fano resonance has been a characteristic feature of interacting quantum systems. The shape of this resonance is distinctively different from that of conventional symmetric resonance curves. Recently, the Fano resonance has been found in plasmonic nanoparticles, photonic crystals, and electromagnetic metamaterials. The steep dispersion of the Fano resonance profile promises applications in sensors, lasing, switching, and nonlinear and slow-light devices. © 2010 Macmillan Publishers Limited. All rights reserved.

Li G.,Data Storage Institute Singapore | Wen C.,Nanyang Technological University
IEEE Transactions on Signal Processing | Year: 2012

In this paper, we consider the parametric version of Wiener systems where both the linear and nonlinear parts are identified with clipped observations in the presence of internal and external noises. Also the static functions are allowed noninvertible. We propose a classification based support vector machine (SVM) and formulate the identification problem as a convex optimization. The solution to the optimization problem converges to the true parameters of the linear system if it is an finite-impulse-resposne (FIR) system, even though clipping reduces a great deal of information about the system characteristics. In identifying a Wiener system with a stable infinite-impulse-response (IIR) system, an FIR system is used to approximate it and the problem is converted to identifying the FIR system together with solving a set of nonlinear equations. This leads to biased estimates of parameters in the IIR system while the bias can be controlled by choosing the order of the approximated FIR system. © 2012 IEEE.

Yu P.,Data Storage Institute Singapore
International Journal of Heat and Mass Transfer | Year: 2012

Detailed numerical simulations are performed for oxygen transfer around and within a circular scaffold for animal cell culture. The oxygen concentration distribution, minimum oxygen concentration within the scaffold and its corresponding location, as well as the Sherwood number are presented at different Darcy numbers, Reynolds numbers and Damkohler numbers. It is found that if the Reynolds number is increased from 1 to 30, the Sherwood number increases 1 time for a Darcy number of 5 × 10 -6 while 34 times for a Darcy number of 5 × 10 -4. The location of the minimum oxygen concentration is close to the centre of the scaffold when the Darcy number is smaller than about 5 × 10 -5 or the Reynolds number is smaller than about 1, especially for the Damkohler number larger than O(10). The present study may provide useful guidance on design of the bioreactor with scaffold as well as choosing optimal operating parameters. © 2012 Elsevier Ltd. All rights reserved.

Sbiaa R.,Data Storage Institute Singapore | Meng H.,Data Storage Institute Singapore | Piramanayagam S.N.,Data Storage Institute Singapore
Physica Status Solidi - Rapid Research Letters | Year: 2011

Materials with perpendicular magnetic anisotropy (PMA) are being investigated for magnetic random access memory (MRAM) and other spintronics applications. This article is an overview of the developments in this topic. At first, a historical overview of the magnetic memory is presented along with the fundamentals of MRAM using the field-assisted scheme. Later on, the principle of spin-transfer torque (STT) is explained briefly along with the STT-MRAM design requirements. Here, it is described that the MRAM design is a challenge where a choice has to be made to meet five criteria, a phenomenon called MRAM pentalemma. The main part of the article focuses on the discussion of materials with PMA. The focus is made first on multilayers such as Co/Pd and Co/Pt which have been widely investigated, followed by the recent observation of PMA in FeCoB. In subsequent sections, the progress in future candidates such as FePt is discussed. The article concludes with a summary of the challenges and future directions in this research topic. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) In this Review, the princple of spin-transfer torque magnetic random access memory (STT-MRAM) is explained: The magnetic tunnel junction device is sandwiched between two electrodes (cross-point architecture). The writing is based on spin torque effect and the reading on tunnelling magneto-resistive effect. In contrast to field-based MRAM, STT-MRAM does not require external magnetic field. Since STT-MRAM is scalable, the transistor scales down with the device size. Materials with perpendicular magnetic anisotropy (PMA) are being investigated for their use in STT-MRAM - multilayers such as Co/Pd and Co/Pt as well as FeCoB and future candidates such as FePt. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fu Y.H.,Data Storage Institute Singapore | Kuznetsov A.I.,Data Storage Institute Singapore | Miroshnichenko A.E.,Australian National University | Yu Y.F.,Data Storage Institute Singapore | Luk'yanchuk B.,Data Storage Institute Singapore
Nature Communications | Year: 2013

Directional light scattering by spherical silicon nanoparticles in the visible spectral range is experimentally demonstrated for the first time. These unique optical properties arise because of simultaneous excitation and mutual interference of magnetic and electric dipole resonances inside a single nanosphere. Such behaviour is similar to Kerker's-type scattering by hypothetic magneto-dielectric particles predicted theoretically three decades ago. Here we show that directivity of the far-field radiation pattern of single silicon spheres can be strongly dependent on the light wavelength and the nanoparticle size. For nanoparticles with sizes ranging from 100 to 200 nm, forward-to-backward scattering ratio above six can be experimentally obtained, making them similar to 'Huygens' sources. Unique optical properties of silicon nanoparticles make them promising for design of novel low-loss visible- and telecom-range metamaterials and nanoantenna devices. © 2013 Macmillan Publishers Limited.

Fu Y.H.,Data Storage Institute Singapore | Zhang J.B.,Data Storage Institute Singapore | Yu Y.F.,Data Storage Institute Singapore | Luk'Yanchuk B.,Data Storage Institute Singapore
ACS Nano | Year: 2012

Figure Persented: In this article, we investigate higher order (quadrupolar, octupolar, hexadecapolar, and triakontadipolar) Fano resonances generated in disk ring (DR) silver plasmonic nanostructures. We find that the higher order Fano resonances are generated when the size of the disk is reduced and falls into a certain range. With dual-disk ring (DDR) nanostructures, a rich set of tunable Fano line shapes is provided. More specifically, we report our observations on the optical behavior of the DDRs including asymmetric cases either in two disks with different sizes or their asymmetric locations inside the ring. In the case of symmetric dual-disk ring (SDDR) nanostructures, we demonstrate that the quadrupolar and the hexadecapolar Fano resonances are suppressed, which can reduce the cross-talk in spectroscopic measurements, while the octupolar and the triakontadipolar Fano resonances are enhanced. The potential of using the studied plasmonic nanostructures as biochemical sensors is evaluated with the figure of merit (FOM) and the contrast ratio (CR). The values of the FOM and the CR achieved using the triakontadipolar Fano resonance in the SDDR are 17 and 57%, respectively. These results indicate that the SDDRs could be developed into a high-performance biochemical sensor in the visible wavelength range. © 2012 American Chemical Society.

Miroshnichenko A.E.,Australian National University | Luk'Yanchuk B.,Data Storage Institute Singapore | Maier S.A.,Imperial College London | Kivshar Y.S.,Australian National University
ACS Nano | Year: 2012

Figure Persented: We propose a novel type of hybrid metal-dielectric structures composed of silicon nanoparticles and split-ring resonators for advanced control of optically induced magnetic response. We reveal that a hybrid "metamolecule" may exhibit a strong distance-dependent magnetic interaction that may flip the magnetization orientation and support "antiferromagnetic" ordering in a hybrid metamaterial created by a periodic lattice of such metamolecules. The propagation of magnetization waves in the hybrid structures opens new ways for manipulating artificial "antiferromagnetic" ordering at high frequencies. © 2011 American Chemical Society.

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