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We present a combined experimental and simulation study of a single self-assembled InGaAs quantum dot coupled to a nearby ($\sim 25nm$) plasmonic antenna. Micro-photoluminescence spectroscopy shows a $\sim 2.4\times$ increase of intensity, which is attributed to spatial far-field redistribution of the emission from the quantum dot-antenna system. Power-dependent studies show similar saturation powers of $2.5\mu W$ for both coupled and uncoupled quantum dot emission in polarization-resolved measurements. Moreover, time-resolved spectroscopy reveals the absence of Purcell-enhancement of the quantum dot coupled to the antenna as compared to an uncoupled dot, yielding comparable exciton lifetimes of $\tau\sim0.5ns$. This observation is supported by numerical simulations, suggesting only minor Purcell-effects of $<2\times$ for emitter-antenna separations $>25nm$. The observed increased emission from a coupled quantum dot-plasmonic antenna system is found to be in good qualitative agreement with numerical simulations and will lead to a better understanding of light-matter-coupling in such novel semiconductor-plasmonic hybrid systems

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Nature Photonics 10, 73 (2016). doi:10.1038/nphoton.2016.5

Author: David Pile

Nature Physics 12, 111 (2016). doi:10.1038/nphys3661

Author: Luke Fleet

Author(s): Xu Fang, Ming Lun Tseng, Din Ping Tsai, and Nikolay I. Zheludev

Thin films are central to modern technologies ranging from semiconductors to metamaterials. The authors observe that by placing a subwavelength thin film at the node of an electromagnetic standing wave, it is possible to separate electric from magnetic dipole terms, or dipole from quadrupole terms, in the absorption spectrum. The technique is twice as sensitive as conventional measurements, functions at very low laser power, and reveals resonances that are invisible to existing spectroscopies. This approach could see application in analytical chemistry, condensed matter physics, nanotechnology, and forensic science.

[Phys. Rev. Applied 5, 014010] Published Wed Jan 27, 2016

Mastering the game of Go with deep neural networks and tree search

Nature 529, 7587 (2016). doi:10.1038/nature16961

Authors: David Silver, Aja Huang, Chris J. Maddison, Arthur Guez, Laurent Sifre, George van den Driessche, Julian Schrittwieser, Ioannis Antonoglou, Veda Panneershelvam, Marc Lanctot, Sander Dieleman, Dominik Grewe, John Nham, Nal Kalchbrenner, Ilya Sutskever, Timothy Lillicrap, Madeleine Leach, Koray Kavukcuoglu, Thore Graepel & Demis Hassabis

The game of Go has long been viewed as the most challenging of classic games for artificial intelligence owing to its enormous search space and the difficulty of evaluating board positions and moves. Here we introduce a new approach to computer Go that uses ‘value

This article reviews the nature and history of the discovery of high-quality natural modes existing on periodic arrays of many subwavelength scatterers; such arrays can be viewed as specific periodically structured open resonators. These grating modes (GMs), like any other natural modes, give rise to the associated resonances in electromagnetic-wave scattering and absorption. Their complex wavelengths are always located very close to (but not exactly at) the well-known Rayleigh anomalies (RAs), determined only by the period and the angle of incidence. This circumstance has long been a reason for their misinterpretation as RAs, especially in the measurements and simulations using low-resolution methods. In the frequency scans of the reflectance or transmittance, GM resonances usually develop as asymmetric Fano-shape spikes. In the optical range, if a grating is made of subwavelength-size noble-metal elements, then GMs exist together with better-known localized surface-plasmon (LSP) modes. Thanks to high tunability and considerably higher Q-factors, the GM resonances can potentially replace the LSP-mode resonances in the design of nanosensors, nanoantennas, and solar-cell nanoabsorbers.

An analysis is presented of scattering of an electromagnetic linearly polarized plane wave by a multilayered sphere. The focus is on obtaining a computational form of the Mie coefficients for the scattered field. A central role is played by ratios of spherical Bessel functions that can be calculated easily, rapidly, and accurately by recurrence relations whose stabilities are demonstrated. Logarithmic derivatives are not employed. A detailed outline is given of a carefully tested computer program for implementing and validating the analysis. Numerous comparisons are given of numerical results obtained with this program with corresponding results in the literature. Important properties of the Mie coefficients and aspects of the scattered field are discussed including the loci of the Mie coefficients in the complex plane; the resonances of the Mie coefficients; the extinction, scattering, and absorption efficiencies of the scattered field; radiation pressure; the Debye series, and the complex angular momentum (CAM) method.

To optimize the interaction between chiral matter and highly twisted light, quantities that can help characterize chiral electromagnetic fields near nanostructures are needed. Here, by analogy with Poynting's theorem, we formulate the time-averaged conservation law of optical chirality in lossy dispersive media and identify the optical chirality flux as an ideal far-field observable for characterizing chiral optical near fields. Bounded by the conservation law, we show that it provides precise information, unavailable from circular dichroism spectroscopy, on the magnitude and handedness of highly twisted fields near nanostructures.

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We investigate the interplay of shape changes and localized surface plasmons in small metal particles with the potential of a large enhancement of the Raman signal from the particles own vibrations. The framework is a geometrical one where we study the change in geometric factors during the vibrational movement. The resulting cross-section is found to be of a detectable order of magnitude however much smaller than the elastic cross-section.

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Metasurfaces are nano-structured devices composed of arrays of subwavelength scatterers (or meta-atoms) that manipulate the wavefront, polarization, or intensity of light. Like other diffractive optical devices, metasurfaces suffer from significant chromatic aberrations that limit their bandwidth. Here, we present a method for designing multiwavelength metasurfaces using unit cells with multiple meta-atoms, or meta-molecules. Transmissive lenses with efficiencies as high as 72% and numerical apertures as high as 0.46 simultaneously operating at 915 nm and 1550 nm are demonstrated. With proper scaling, these devices can be used in applications where operation at distinct known wavelengths is required, like various fluorescence microscopy techniques.

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Author(s): D. Bouchet, D. Cao, R. Carminati, Y. De Wilde, and V. Krachmalnicoff

The range of energies that can be transferred between two molecules can be increased by a factor of almost one thousand using a simple silver mirror.

[Phys. Rev. Lett. 116, 037401] Published Thu Jan 21, 2016

Article

Devices with greater freedom are desired in nanophotonics. Here, the authors demonstrate theoretically and experimentally that the generalized Brewster effect can be observed in an all-dielectric metasurface potentially for any angle, wavelength and polarization, due to electric and magnetic dipole interference.

Nature Communications doi: 10.1038/ncomms10362

Authors: Ramón Paniagua-Domínguez, Ye Feng Yu, Andrey E. Miroshnichenko, Leonid A. Krivitsky, Yuan Hsing Fu, Vytautas Valuckas, Leonard Gonzaga, Yeow Teck Toh, Anthony Yew Seng Kay, Boris Luk’yanchuk, Arseniy I. Kuznetsov

Incandescent light bulbs have changed little since Thomas Edison perfected them in 1878. But now, researchers report that they've tripled the efficiency of an incandescent, making it nearly as efficient as a commercial LED. They did so by reworking the light bulb's metal light emitter into a flat sheet and flanking it on either side with nanostructured mirrors. The mirrors allow visible light to pass through, but they reflect infrared light back to the emitter, where it's absorbed and some of the energy is re-emitted as visible light. The researchers now hope to improve their mirrors to make their new-age incandescents far more efficient than today's best LEDs and compact fluorescents. That could save energy and reduce carbon dioxide emissions, while still giving us the warm, yellowish white glow we love from incandescent lights. Author: Robert F. Service

Plasmonics offer an exciting way to mediate the interaction between light and matter, allowing strong field enhancement and confinement, large absorption and scattering at resonance. However, simultaneous realization of ultra-narrow band perfect absorption and electromagnetic field enhancement is challenging due to the intrinsic high optical losses and radiative damping in metals. Here, we propose an all-metal plasmonic absorber with an absorption bandwidth less than 8nm and polarization insensitive absorptivity exceeding 99%. Unlike traditional Metal-Dielectric-Metal configurations, we demonstrate that the narrowband perfect absorption and field enhancement are ascribed to the vertical gap plasmonic mode in the deep subwavelength scale, which has a high quality factor of 120 and mode volume of about 10^-4*({\lambda}/n)^3 . Based on the coupled mode theory, we verify that the diluted field enhancement is proportional to the absorption, and thus perfect absorption is critical to maximum field enhancement. In addition, the proposed perfect absorber can be operated as a refractive index sensor with a sensitivity of 885nm/RIU and figure of merit as high as 110. It provides a new design strategy for narrow band perfect absorption and local field enhancement, and has potential applications in biosensors, filters and nonlinear optics.

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Nature Photonics 10, 2 (2016). doi:10.1038/nphoton.2015.260

Author: Oliver Graydon

Nature Nanotechnology 11, 23 (2016). doi:10.1038/nnano.2015.304

Authors: Saman Jahani & Zubin Jacob

Nature Nanotechnology 11, 1 (2016). doi:10.1038/nnano.2015.333

Developing useful methods to control light–matter interactions at the nanoscale requires an appreciation of the needs of industry and innovative approaches that go beyond plasmonics.