Volume 8 Issue 4, April 2014

The advent of novel fluorophores that harness thermally activated energy transfer processes is resulting in a new breed of highly efficient organic light-emitting diodes.

The introduction of a dressing beam to extend the reach of filaments promises a wealth of new applications that extend beyond the laboratory scale.

A new experiment demonstrates the first unequivocally quantum two-particle interference with surface plasmons. Subwavelength optical quantum information processing may be just around the corner.

Guaranteed entanglement sharing over long distances can be verified by violating a Bell inequality. That's a tricky enough proposition in itself, but what if more than two parties are involved?

Hollow-core photonic crystal fibres are attractive because they exhibit pressure-adjustable normal or anomalous dispersion, low-loss guidance, very low nonlinearity and high damage threshold. This Review overviews nonlinear optical phenomena in gas-filled, hollow-core photonic crystal fibres that may lead to a new generation of versatile and efficient pulse-compression devices and gas-based light sources.

An optical memory is demonstrated in a kagome photonic crystal fibre whose 26-μm-diameter hollow core is loaded with cesium atoms. Gigahertz-bandwidth light is stored using a far-detuned Raman interaction. It has a memory efficiency is 27 ± 1% and a signal-to-noise ratio of 2.6:1 — the highest at the single-photon level of any memory at room temperature.

Violation of the classical bound of the three-particle Mermin inequality by nine standard deviations is experimentally demonstrated by closing both the locality and freedom-of-choice loopholes; only the fair-sampling assumption is required. To achieve this, a light source for producing entangled multiphoton states and measurement technologies for precise timing and efficient detection were developed.

Plasma channels induced in air by femtosecond-laser filamentation are useful for many applications, including attosecond physics and spectroscopy and remote sensing. By appropriately employing a surrounding auxiliary dressing beam to continuously supply energy to the filament, the natural range of the plasma column has been extended by at least one order of magnitude.

By exploiting a self-bending point spread function based on Airy beams, a three-dimensional super-resolution fluorescence imaging is realized. A three-dimensional localization precision in the range 10–15 nm was obtained at an imaging depth of 3 µm from ∼2,000 photons per localization.

Mid-infrared spectroscopy with nanometre spatial resolution is highly desired for materials and life sciences applications. A nanoscale mid-infrared spectrometer is demonstrated that detects mechanical forces exerted by molecules on an atomic force microscope tip upon light excitation. It operates under ambient conditions with a high sensitivity and a spatial resolution of better than 25 nm.

The first observation of a third-order process induced by an X-ray beam from a free-electron laser is realized in germanium using a 5.6-keV X-ray beam. Two-photon absorption is confirmed, suggesting that X-ray analogues of other third-order nonlinear processes may be available for exploitation in X-ray experiments.

Researchers demonstrate unequivocal quantum interference between plasmons in a Hong–Ou–Mandel experiment. The results may be important for quantum information applications of plasmonics.

A simple experiment enables simultaneous long-range spatial structuring of a cold atomic cloud and an optical pump field, with an adjustable length scale.

Blue organic light-emitting diodes that harness thermally activated delayed fluorescence are realized with an external quantum efficiency of 19.5% and reduced roll-off at high luminance.

Emulation of noiseless linear amplification of quantum states of light is demonstrated by post-selection of measurement data obtained by heterodyne detection. Using this protocol, Einstein–Podolsky–Rosen entanglement is recovered after its degradation by transmission loss. This protocol is applicable to other quantum communication protocols, including teleportation and remote state preparation.

A hollow-core optical fibre filled with warm caesium atoms can temporarily store the properties of photons. Michael Sprague from the University of Oxford, UK, explains to Nature Photonics how this optical memory could be a useful building block for fibre-based quantum optics.