Research articles

Bright, efficient and low-drive-voltage colloidal quantum-dot LEDs that have a crosslinked-polymer quantum-dot layer, and use a sol–gel titanium oxide layer for electron transport, are reported. Integrating the QD-LEDs with a silicon thin-film transistor backplane results in a QD-LED display.

Using two coherent broadband fibre-laser frequency comb sources, a coherent laser ranging system for absolute distance measurements is demonstrated. Its combination of precision, speed and long range may prove particularly useful for space-based sciences.

A small angular deviation of the law of reflection has been previously predicted for a light beam, and is a consequence of the angular dependence of the reflectivity. Experimental proof of such a deviation at near-infrared wavelengths is now reported.

Near-infrared imaging with solution-processed organic–inorganic hybrid photodiodes is demonstrated for the first time. The hybrid bulk-heterojunction photodiodes contain PbS nanocrystalline quantum dots as sensitizers for the detection of light of up to 1.8 µm in wavelength, have a minimum lifetime of one year, and external quantum efficiencies of up to 51%.

Whether the electromagnetic fields in random lasers are localized or extended is a topic of ongoing debate. Now, the localization of modes in micro-structured ZnO powder is experimentally determined and lasing from both kinds of modes (localized and extended) shown to exist simultaneously.

A polymer solar-cell based on a bulk hetereojunction design with an internal quantum efficiency of over 90% across the visible spectrum (425 nm to 575 nm) is reported. The device exhibits a power-conversion efficiency of 6% under standard air-mass 1.5 global illumination tests.

An ambient light display based on electrofluidic control of coloured pigment fluids is reported. Electromechanical pressure is used to move the pigment from a reservoir to the entire surface of a pixel on a timescale of tens of milliseconds. The display has a white light reflectivity of 55%.

Evolution of the infrared near-fields of progressively loaded gap antennas is probed using near-field microscopy. The amplitude and phase is shown to be controlled by the antenna loading and the changes can be understood within the framework of circuit theory.

Electrical detection and characterization of gap plasmons is achieved by means of an integrated metal–semiconductor–metal photodetector. Integration of electro–optical components in metallic waveguides may lead to active high-bandwidth on-chip nano-optical circuits.

The use of slow light for enhancing a nonlinear optical process in a two-dimensional silicon photonic-crystal waveguide is demonstrated. More specifically, green emission by third-harmonic generation is obtained, highlighting yet another functionality of silicon photonics chips.

By applying a magnetic field to an atomic vapour, it is shown that the large bandwidth of off-resonance slow-light media can be combined with the Faraday effect to realize a high-bandwidth dispersive probe for atomic systems. This will open up the possibility of probing atomic dynamics on a nanosecond timescale.

Imaging through a nonlinear medium can be difficult because signals distort as they propagate through it owing to intensity-dependent phase changes. Here, digital reconstruction of optical spatial beams propagating in a nonlinear medium is presented, which could help the understanding of coupled-wave dynamics and suggest new image-processing techniques.

Using a near-field transducer with efficient optical energy transfer, researchers demonstrate proof-of-principle heat-assisted magnetic recording with multi-track data density of ∼375 Tb m⁻².

A silicon–organic hybrid slot waveguide with a strong optical nonlinearity is demonstrated to perform ultrafast all-optical demultiplexing of high-bit-rate data streams. The approach could form the basis of compact high-speed optical processing units for future communication networks.

Blue light-emitting diodes with a light extraction efficiency of 73% are reported. The InGaN–GaN devices use a photonic-crystal structure for superior optical mode control; their performance has been characterized experimentally and modelled theoretically.

Based on a far-field fluorescence-based optical super-resolution scheme – stimulated emission depletion microscopy – scientists resolve densely packed individual fluorescent colour centres inside crystals with a far-field spatial resolution of 5.8 nm without photobleaching. The approach will support future studies of solid-state single-photon sources and quantum optics.

Controlling the orientation of the constituent parts of a metamaterial enables the creation of a new family of optical stereoisomer materials that have an electromagnetic response that can be carefully tailored.

The effect of a tiny gap in a metal substrate on incident terahertz radiation in the regime where the gap's dimensions are smaller than the metal's skin-depth are investigated. The results and theoretical analysis show that the gap acts as a capacitor charged by light-induced currents, and dramatically enhances the local electric field.

Using a single layer of electrically controlled metamaterial, researchers have achieved active control of the phase of terahertz waves and demonstrated high-speed broadband modulation.

A system based on a highly nonlinear planar chalcogenide waveguide is demonstrated to be able to perform radio-frequency spectral measurements with a terahertz bandwidth. High bit-rate tests show that the chip-based system is potentially useful for ultrafast signal processing.