gevero

Nature Materials. doi:10.1038/nmat4694

Authors: Xiaoyu Zheng, William Smith, Julie Jackson, Bryan Moran, Huachen Cui, Da Chen, Jianchao Ye, Nicholas Fang, Nicholas Rodriguez, Todd Weisgraber & Christopher M. Spadaccini

On the one hand, electromagnetic dual particles preserve the helicity of light upon interaction. On the other hand, chiral particles respond differently to light of opposite helicity. These two properties on their own constitute a source of fascination. Their combined action, however, is less explored. Here, we study on analytical grounds the force and torque as well as the optical cross sections of dual chiral particles in the dipolar approximation exerted by a particular wave of well-defined helicity: A circularly polarized plane wave. We put emphasis on particles that possess a maximally electromagnetic chiral and hence dual response. Besides the analytical insights, we also investigate the exerted optical force and torque on a real particle at the example of a metallic helix that is designed to approach the maximal electromagnetic chirality condition. Various applications in the context of optical sorting but also nanorobotics can be foreseen considering the particles studied in this contribution.

We reveal that an isotropic homogeneous subwavelength particle with a high refractive index can produce ultra-weak total scattering due to vanishing contribution of the electric dipole moment. This effect can be explained with the help of the Fano resonance and scattering efficiency associated with the excitation of an anapole mode. The latter is a nonradiative mode emerging from destructive interference of electric and toroidal dipole moments, and it can be employed for a design of highly transparent optical materials.

Article

Mantis shrimps are known to display large pitch, yaw and torsional eye rotations. Here, the authors show that these eye movements allow mantis shrimp to orientate particular photoreceptors in order to better discriminate the polarization of light.

Nature Communications doi: 10.1038/ncomms12140

Authors: Ilse M. Daly, Martin J. How, Julian C. Partridge, Shelby E. Temple, N. Justin Marshall, Thomas W. Cronin, Nicholas W. Roberts

Single-molecule strong coupling at room temperature in plasmonic nanocavities

Nature 535, 7610 (2016). doi:10.1038/nature17974

Authors: Rohit Chikkaraddy, Bart de Nijs, Felix Benz, Steven J. Barrow, Oren A. Scherman, Edina Rosta, Angela Demetriadou, Peter Fox, Ortwin Hess & Jeremy J. Baumberg

Photon emitters placed in an optical cavity experience an environment that changes how they are coupled to the surrounding light field. In the weak-coupling regime, the extraction of light from the emitter is enhanced. But more profound effects emerge when single-emitter strong coupling occurs: mixed states are produced that are part light, part matter, forming building blocks for quantum information systems and for ultralow-power switches and lasers. Such cavity quantum electrodynamics has until now been the preserve of low temperatures and complicated fabrication methods, compromising its use. Here, by scaling the cavity volume to less than 40 cubic nanometres and using host–guest chemistry to align one to ten protectively isolated methylene-blue molecules, we reach the strong-coupling regime at room temperature and in ambient conditions. Dispersion curves from more than 50 such plasmonic nanocavities display characteristic light–matter mixing, with Rabi frequencies of 300 millielectronvolts for ten methylene-blue molecules, decreasing to 90 millielectronvolts for single molecules—matching quantitative models. Statistical analysis of vibrational spectroscopy time series and dark-field scattering spectra provides evidence of single-molecule strong coupling. This dressing of molecules with light can modify photochemistry, opening up the exploration of complex natural processes such as photosynthesis and the possibility of manipulating chemical bonds.

Let’s make peer review scientific

Nature 535, 7610 (2016). doi:10.1038/535031a

Author: Drummond Rennie

Thirty years on from the first congress on peer review, Drummond Rennie reflects on the improvements brought about by research into the process — and calls for more.

UK scientists in limbo after Brexit shock

Nature 534, 7609 (2016). http://www.nature.com/doifinder/10.1038/534597a

Authors: Alison Abbott, Daniel Cressey & Richard Van Noorden

Researchers organize to lobby for science as country prepares for life outside the EU.

ArXiv preprint server plans multimillion-dollar overhaul

Nature 534, 7609 (2016). http://www.nature.com/doifinder/10.1038/534602a

Author: Richard Van Noorden

Users urge caution in revamp of service at the heart of physics.

Achievement of all-optical ultrafast signal modulation and routing by a low-loss nanodevice is a crucial step towards an ultracompact optical chip with high performance. Here, we propose a specifically designed silicon dimer nanoantenna, which is tunable via photoexcitation of dense electron-hole plasma with ultrafast relaxation rate. Basing on this concept, we demonstrate the effect of beam steering up to 20 degrees via simple variation of incident intensity, being suitable for ultrafast light routing in an optical chip. The effect is demonstrated both in the visible and near-IR spectral regions for silicon and germanium based nanoantennas. We also reveal the effect of electron-hole plasma photoexcitation on local density of states (LDOS) in the dimer gap and find that the orientation averaged LDOS can be altered by 50\%, whereas modification of the projected LDOS can be even more dramatic: almost 500\% for transverse dipole orientation. Moreover, our analytical model sheds light on transient dynamics of the studied nonlinear nanoantennas, yielding all temporal characteristics of the proposed ultrafast nanodevice. The proposed concept paves the ways to creation of low-loss, ultrafast, and compact devices for optical signal modulation and routing.

Plasmonics enables deep-subwavelength concentration of light and has become important for fundamental studies as well as real-life applications. Two major existing platforms of plasmonics are metallic nanoparticles and metallic films. Metallic nanoparticles allow efficient coupling to far field radiation, yet their synthesis typically leads to poor material quality. Metallic films offer substantially higher quality materials, but their coupling to radiation is typically jeopardized due to the large momentum mismatch with free space. Here, we propose and theoretically investigate optically thin metallic films as an ideal platform for high-radiative-efficiency plasmonics. For far-field scattering, adding a thin high-quality metallic substrate enables a higher quality factor while maintaining the localization and tunability that the nanoparticle provides. For near-field spontaneous emission, a thin metallic substrate, of high quality or not, greatly improves the field overlap between the emitter environment and propagating surface plasmons, enabling high-Purcell (total enhancement > $10^4$), high-quantum-yield (> 50 %) spontaneous emission, even as the gap size vanishes (3$\sim$5 nm). The enhancement has almost spatially independent efficiency and does not suffer from quenching effects that commonly exist in previous structures.

Photoluminescence is a phenomenon of significant interest due to its wide range of technological applications in plasmonics, nanolasers, spasers, lasing spasers, loss compensation and gain in metamaterials, and luminescent media. Nanostructured materials are known to have very different luminescence characteristics to bulk samples or planar films. Here we show that by engineering a nanostructured meta-surface, we can choose the position of photoluminescence absorption and emission lines of thin gold films. The nanostructuring also aids to strong enhancement of the emission from gold, by a factor of 76 in our experiments. This enhancement is determined by the relative position of the engineered absorption and emission lines to the exciting laser wavelength and the intrinsic properties of the constituent material. These luminescence-engineered materials combined with a resonant material, as in the lasing spaser, or with the power of reconfigurable metamaterials promise huge potential as tunable nanoscale light sources.

Author(s): Martin Fruhnert, Alessio Monti, Ivan Fernandez-Corbaton, Andrea Alù, Alessandro Toscano, Filiberto Bilotti, and Carsten Rockstuhl

Rendering arbitrary objects invisible is currently of great interest in photonics. While there are some optical tricks to hide macroscopic objects, such as camouflaging and mimetics, true invisibility remains out of reach. However, for sufficiently small objects one can use advanced techniques to prevent their detection at least at discrete wavelengths. The scattered light is suppressed, as envisioned using the recently developed scattering cancellation technique. At optical frequencies, metallic nanoparticles that mantle a small object do the desired job. However, tuning the operational frequency of such a mantle cloak remained a challenge. The authors here solve this problem by using silver ellipsoids instead of spheres. Depending on the axis ratio, the cloaking frequency is tunable throughout the entire visible spectrum. The cloak performance has been rigorously analyzed using the T-matrix method. It is envisioned that the optimized structure opens the door to many applications where the scattering signal will be suppressed at a predefined wavelength, e.g., to suppress the cross-talk between adjacent optical nanoantennas or the spurious signal from a tip in a near-field optical microscope.

[Phys. Rev. B 93, 245127] Published Mon Jun 13, 2016

We study the local field enhancement properties of self-similar nanolenses and compare the obtained results with the performance of standard dimer nanoantennas. We report that, despite the additional structural complexity, self-similar nanolenses are unable to provide significant improvements over the field enhancement performance of standard plasmonic dimers.

Review

Recent work has shown that quantum mechanical effects in plasmonic nanogap structures become important as the gap distances approach the subnanometre length-scale. Here, the authors review the major findings which challenge the classical picture of these structures and discuss future directions for the field.

Nature Communications doi: 10.1038/ncomms11495

Authors: Wenqi Zhu, Ruben Esteban, Andrei G. Borisov, Jeremy J. Baumberg, Peter Nordlander, Henri J. Lezec, Javier Aizpurua, Kenneth B. Crozier