Articles in 2011

Researchers demonstrate a high-efficiency polymer solar cell whose device architecture is compatible with a large-scale roll-to-roll process. Enhanced charge collection in the inverted polymer solar cell design and certified power conversion efficiencies of around 7.4% are reported.

Scientists demonstrate strong coupling between distant nanocavities separated by more than 100 wavelengths as well as dynamic control over the coupling state. The strong coupling state can be stopped on demand by irradiating one of the nanocavities with a control pulse, thus freezing the photon state.

Researchers demonstrate a reconfigurable integrated quantum photonic circuit. The device comprises a two-qubit entangling gate, several Hadamard-like gates and eight variable phase shifters. The set-up is used to generate entangled states, violate a Bell-type inequality with a continuum of partially entangled states and demonstrate the generation of arbitrary one-qubit mixed states.

Using laser-driven spinning birefringent spheres to create a localized microfluidic flow, scientists show that they can control the direction of growth of individual nerve fibres. The approach is potentially useful for the development of nerve systems, as well as for nerve repair and regeneration.

Scientists present the first experimental observations of bright polariton solitons in a strongly coupled semiconductor microcavity. The findings should pave the way to the investigation of a variety of fundamental phenomena, such as interactions between solitons with different spins and the formation of soliton molecules.

Researcher demonstrate the line-by-line pulse shaping of frequency combs generated in silicon nitride ring resonators, and observe two distinct paths to comb formation that exhibit strikingly different time domain behaviours.

Researchers use a pre-orienting layer to achieve nearly single-crystalline GaN pyramidal arrays on amorphous glass substrates. The polycrystalline morphology can be controlled by placing a hole-patterned SiO₂ layer on the low-temperature GaN nucleation layer. Light-emitting diodes fabricated by this technique exhibited a luminance of 600 cd m⁻².

Re-absorption losses in luminescent solar concentrators cause concentration performances to be around ten times less than the ideal value. Researchers have now reduced re-absorption by forcing the emission in one region to be off-resonant with the other regions, achieving a two-fold enhancement in concentration performance over conventional devices.

Researchers demonstrate fast, single-qubit gates using a sequence of 13 ps pulses. Two vertically stacked InAs/GaAs quantum dots were coupled through coherent tunnelling and charged with controlled numbers of holes. The interaction between hole spins was investigated by Ramsey fringe experiments, showing a tunable interaction range of tens of gigahertz.

Surface-enhanced Raman sensors often rely on random chance for molecules to come near optical hotspots. Here, researchers use super-hydrophobic artificial surfaces and evaporation to direct molecules to plasmonic light-focusing structures. Molecules can be localized and detected even at attomolar concentrations.

Researchers demonstrate two-stage laser stabilization based on a combination of Fabry–Pérot and spectral-hole burning techniques. The laser was first pre-stabilized using Fabry–Pérot cavities and then modulated to address a spectral-hole pattern in Eu³⁺:Y₂SiO₅. Taking advantage of the low sensitivity of the spectral holes to environmental perturbations, the researchers obtained a fractional frequency stability of 6 × 10⁻¹⁶

Researchers show that dispersed functionalized graphene can exhibit broadband nonlinear optical absorption at fluences well below the damage threshold. An optical energy-limiting onset benchmark of 10 mJ cm⁻² at a linear transmittance of 70% was obtained for nanosecond visible and near-infrared pulses. The findings shed light on the formation of practical thin films with broadband optical limiting characteristics.

Scientists experimentally demonstrate a reconfigurable all-optical isolator based on the optical excitation of a gigahertz guided acoustic mode in a micrometre-sized photonic crystal fibre core. The work is expected to benefit advanced optical communications and all-optical signal-processing systems.

Researchers use extremely non-degenerate photon pairs to achieve two-photon absorption at levels 100-1,000 times that of degenerate two-photon absorption in direct-gap semiconductors. The technique enables the gated detection of sub-bandgap and sub-100-pJ mid-infrared radiation using large-bandgap detectors at room temperature.

Researchers demonstrate solution-processed light-emitting diodes based on a quantum-dot emissive layer between an organic hole-transport layer and an electron-transport layer of ZnO nanoparticles. The device achieves a luminance of 68,000 cd m⁻² and power efficiencies of up to 8.2 lm W⁻¹.

Researchers have fired ultracold-atom Bose–Einstein condensates towards the submicrometre-featured potentials formed by the optical near-fields of surface plasmons. The strength and structural dependence of the optical near-fields were determined from the reflection of cold atoms. It is hoped that the work paves the way towards plasmonic guiding and the manipulation of cold atoms.

Researchers experimentally demonstrate that light propagating through a path-averaged zero-index dielectric medium can have zero phase delay, despite a non-zero physical path length. The medium is a superlattice consisting of layers of negative-refractive-index dielectric photonic crystals and positive-refractive-index homogeneous dielectric media.

Scientists experimentally demonstrate an optical-fibre-based non-degenerate phase-sensitive amplifier link that offers broadband amplification, signal modulation-format independence and lower noise than links based on conventional erbium-doped fibre amplifiers.

Scientists show that spatiotemporal focusing and compression of non-Fourier-limited pulses through scattering media can be achieved by manipulating only the spatial degrees of freedom of the incident wavefront. This technique is potentially attractive for optical manipulation and nonlinear imaging in scattering media.

Researchers demonstrate the real-time generation and fast Fourier transformation of 10.8 Tbit s⁻¹ and 26 Tbit s⁻¹ line-rate optical frequency-division multiplexed signals, using an all-optical fast Fourier transform scheme based on cascaded delay interferometers and a time gate.