The technologies of heating, photovoltaics, water photocatalysis and artificial photosynthesis depend on the absorption of light and novel approaches such as coherent absorption from a standing wave promise total dissipation of energy. Extending the control of absorption down to very low light levels and eventually to the single-photon regime is of great interest and yet remains largely unexplored. Here we demonstrate the coherent absorption of single photons in a deeply subwavelength 50% absorber. We show that while the absorption of photons from a travelling wave is probabilistic, standing wave absorption can be observed deterministically, with nearly unitary probability of coupling a photon into a mode of the material, for example, a localized plasmon when this is a metamaterial excited at the plasmon resonance. These results bring a better understanding of the coherent absorption process, which is of central importance for light harvesting, detection, sensing and photonic data processing applications.

The ability to control the wavefront of light is fundamental to focusing and redistribution of light, enabling many applications from imaging to spectroscopy. Wave interaction on highly nonlinear photorefractive materials is essentially the only established technology allowing the dynamic control of the wavefront of a light beam with another beam of light, but it is slow and requires large optical power. Here we report a proof-of-principle demonstration of a new technology for two-dimensional (2D) control of light with light based on the coherent interaction of optical beams on highly absorbing plasmonic metasurfaces. We illustrate this by performing 2D all-optical logical operations (AND, XOR and OR) and image processing. Our approach offers diffraction-limited resolution, potentially at arbitrarily-low intensity levels and with 100 THz bandwidth, thus promising new applications in space-division multiplexing, adaptive optics, image correction, processing and recognition, 2D binary optical data processing and reconfigurable optical devices.

Electro- and magneto-optical phenomena play key roles in photonic technology enabling light modulators, optical data storage, sensors and numerous spectroscopic techniques. Optical effects, linear and quadratic in external electric and magnetic field are widely known and comprehensively studied. However, optical phenomena that depend on the simultaneous application of external electric and magnetic fields in conventional media are barely detectable and technologically insignificant. Here we report that a large reciprocal magneto-electro-optical effect can be observed in metamaterials. In an artificial chevron nanowire structure fabricated on an elastic nano-membrane, the Lorentz force drives reversible transmission changes on application of a fraction of a volt when the structure is placed in a fraction-of-tesla magnetic field. We show that magneto-electro-optical modulation can be driven to hundreds of thousands of cycles per second promising applications in magneto-electro-optical modulators and field sensors at nano-tesla levels.

The exponential growth of telecommunications bandwidth will require next generation optical networks, where multiple spatial information channels will be transmitted in parallel. To realise the full potential of parallel optical data channels, fast and scalable multichannel solutions for processing of optical data are of paramount importance. Established solutions based on the nonlinear wave interaction in photorefractive materials are slow. Here we experimentally demonstrate all-optical logical operations between pairs of simulated spatially multiplexed information channels using the coherent interaction of light with light on a plasmonic metamaterial. The approach is suitable for fiber implementation and—in principle—operates with diffraction-limited spatial resolution, 100 THz bandwidth, and arbitrarily low intensities, thus promising ultrafast, low-power solutions for all-optical parallel data processing.

We demonstrate that spatial arrangement and optical properties of metamaterial nanostructures can be controlled dynamically using currents and magnetic fields. Mechanical deformation of metamaterial arrays is driven by both resistive heating of bimorph nanostructures and the Lorentz force that acts on charges moving in a magnetic field. With electrically controlled transmission changes of up to 50% at sub-mW power levels, our approaches offer high contrast solutions for dynamic control of metamaterial functionalities in optoelectronic devices.Dynamic control over metamaterial functionalities has become a major research challenge, as the numerous novel and dramatically enhanced functionalities that metamaterials can provide are usually narrow-band and fixed. The use of superconductors [1,2], phase change media [3][4][5], liquid crystals [6][7][8][9], nonlinear materials [10][11][12][13], graphene [14,15], and coherent optical interactions [16,17] has been investigated to achieve metamaterial properties tunable via temperature, external fields, light intensity or phase, or carrier injection [18,19] [27,28]. However, the latter require large ambient temperature changes or engage irreversible structural transitions to achieve significant optical contrast. Therefore, a practical solution for reversible large-range tuning of photonic metamaterial properties is still needed. Here we demonstrate that reconfigurable photonic metamaterials controlled by electrical currents and magnetic fields provide such a practical solution for reversible large-range tuning and modulation of optical metamaterial functionalities. Our approach takes advantage of the changing balance of forces at the nanoscale, where bilayers of nanoscale thickness bend strongly in response to temperature changes and weak elastic forces allow the magnetic Lorentz force to cause substantial deformation of the picogram-scale moving parts.Optical properties of metallic nanostructures, such as the metamaterial investigated here, are determined by the localized plasmonic response of coupled oscillations of conduction electrons and the electromagnetic nearfield induced by the incident light. In this work, dynamic control over metamaterial optical properties is achieved by exploiting the strong electromagnetic inter- * Electronic address: jpv1f11@orc.soton.ac. actions between the metamaterial building blocks, the metamolecules. By changing the physical arrangement of the nanoscale metamolecules we change their coupling and therefore the optical properties of the metamaterial array. Synchronous rearrangement of about 1000 plasmonic resonators at the nanoscale is achieved exploiting two simple physical principles, (i) bilayers consisting of materials with different thermal expansion coefficients will bend in response to temperature changes and (ii) electric charges moving in a magnetic field will be subject to the magnetic Lorentz force, see Fig 1. Selective resistive heating of alternating bridges and thus their deformation by differential thermal expansion, as w...

Quantum nonlocality, i.e., the presence of strong correlations in spatially separated systems that are forbidden by local realism, lies at the heart of quantum communications and quantum computing. Here, we use polarization-entangled photon pairs to demonstrate a nonlocal interaction of light with a plasmonic structure. Through the detection of one photon with a polarization-sensitive device, we can prevent or allow absorption of a second, remotely located photon. We demonstrate this with pairs of entangled photons in polarization, one of which is coupled into a plasmon of a thin metamaterial absorber in the path of a standing wave of an interferometer. Thus, we realize a quantum eraser experiment using photons and plasmonic resonances from metamaterials that promises opportunities for probabilistic quantum gating and controlling plasmon–photon conversion and entanglement. Moreover, by using the so-called coherent perfect absorption effect, we can expect near-perfect interaction.

Semiconductor nanowire based devices are amongst the most promising structures to meet the current challenges of electronics, optics and photonics. Due to their high surface-volume ratio and excellent optical and electrical properties, low power, high efficiency and high-density devices can be achieved. This is of major importance for environmental issues and economic impact. Semiconductor nanowires have been used to fabricate high performance devices, including detectors, solar cells and transistors. Here we demonstrate a technique to transfer large area nanowire arrays to flexible substrates whilst retaining their excellent quantum efficiency in emission. Starting with a defect-free self-catalysed molecular beam epitaxy (MBE) sample grown on a Si substrate, GaAs core-shell nanowires are embedded in a dielectric, removed by reactive ion beam etching and transferred to a plastic substrate. The original structural and optical properties, including the vertical orientation, of the nanowires are retained in the final plastic substrate structure. Nanowire emission is observed for all stages

and epoxy-resin casting.[ 19 ] Soft lithography, [ 12 ] femtosecond laser ablation, [ 13 ] and digital micromirror device projection printing [ 14 ] have allowed the fabrication of negative Poisson's ratio structures with characteristic sizes of hundreds of micrometers. Smaller dielectric auxetics with unit cells on the order of 100 µm have been made by laser micromachining, [ 15 ] while dielectric auxetics with a characteristic size of 10 µm have been realized by direct laser writing. [ 16 ] However, negative Poisson's ratio materials with nanoscale lattice para meters cannot be fabricated using such techniques due to their limited resolution and the complexity of auxetic designs. Nevertheless, nanoscale auxetics would be particularly interesting as optical materials, considering that the combination of transformation optics concepts [ 20 ] with dielectric properties of auxetic meta materials [ 19,[21][22][23][24][25] already promises better electromagnetic cloaking devices for microwaves. [ 26,27 ] Here, we realize micro-and nanoscale metamaterial structures and demonstrate negative Poisson's ratios by mechanical actuation ( Figure 1 ). Our nano-auxetic metamaterials are based on the re-entrant honeycomb design, which is known for auxetic properties for a wide range of beam thicknesses, sizes, and angles. [ 11 ] Inspired by recent work in the fi eld of nanomechanical photonic devices, [ 28 ] nanomembrane technology was used to fabricate auxetics with lattice parameters in the range from a few micrometers to hundreds of nanometers. Nanomembrane technology has already provided simple and effi cient solutions for reconfi guration of nanoscale structures that are not auxetic, enabling nanomechanical devices and sensors. In particular, engineered resonant optical properties and anisotropic light modulation with up to 50% optical contrast has been demonstrated with reconfi gurable metamaterials actuated by thermal, [ 29 ] electric, [ 30 ] and magnetic [ 31 ] signals, and fabricated from plasmonic-thin-fi lm-coated nanomembranes.The auxetic materials are shown by Figure 2 and were fabricated by thermally evaporating a 60 nm-thick gold plasmonic layer on a commercially available silicon nitride membrane of 50 nm thickness and then milling the re-entrant honeycomb structure through both layers using a gallium-focused ion-beam system (Helios 600 NanoLab by FEI). All structures were milled with an ion-beam energy of 30 keV. Infrared auxetic metamaterial microstructures were fabricated with 70 pA ion-beam current and a spot size of 21 nm, while nano-auxetic structures were milled with a reduced ion current of 9 pA and a smaller spot size of 12 nm. The honeycomb pattern has a rhombic unit cell and wallpaper symmetry group cmm . [ 32 ] For simplicity, we specify the smallest rectangular cell, p x × p y , that describes each structure, where the periodicities p x and p y along x and y correspond to the diagonals of the elementary rhombic unit cell, see Auxetics, materials with a negative Poisson's ratio, are rare in nature. ...