Research articles

An efficient source of entangled photons generated in an event-ready manner by conditioned detection of auxiliary photons is reported. A fidelity better than 87% and a state preparation efficiency of 45% are obtained. The scheme could offer promising applications in essential photonics-based quantum information tasks, and represents a particularly important development in the realization of optical quantum computing.

Using probe and pump waves derived from ultra-compact telecom optical fibre sources, scientists perform four-wave mixing in silicon waveguides in the spectral region beyond 2 µm, achieving mid-infrared wavelength generation of 2388 nm over a bandwidth of 630 nm on a silicon chip.

By taking advantage of the absorption reduction at wavelengths approaching the two-photon absorption bandedge of 2,200 nm, scientists demonstrate a mid-infrared silicon optical parametric amplifier that exhibits broadband gain as large as 25.4 dB and a net off-chip amplification of 13 dB using only an ultra-compact 4-mm silicon chip.

Using standard silica optical fibres, scientists observe temporal cavity solitons — packets of light persisting in a continuously driven nonlinear resonator. Cavity solitons 4 ps long are reported and used to demonstrate storage of a data stream for more than a second. The findings represent one of the simplest examples of self-organization phenomena in nonlinear optics.

Researchers demonstrate free-space quantum teleportation through 16 kilometres of air. The results may pave the way for space-based experiments and global scale quantum communication applications.

Distortions in a propagating optical wavefront — known as aberrations — prevent the achievement of a diffraction-limited beam spot. A generic in situ wavefront correction method based on complex modulation is demonstrated, allowing compensation for all aberrations along the whole optical train. The scheme is used for direct trapping through highly turbid and diffusive media, opening up new applications for optical micromanipulation in colloidal and biological physics.

Scientists demonstrate a simple self-referenced feed-forward approach for stabilizing the carrier–envelope phase of femtosecond light pulses. Twelve attoseconds of residual timing jitter below the atomic unit of time is achieved, surpassing the precision of previous methods by more than a factor of five.

Microscale planar optical elements based on high-reflectivity, non-periodic gratings provide a compact and convenient means for focusing and shaping light.

Using a composite photonic-crystal structure composed of both a square and rectangular lattice, scientists successfully realize an on-chip semiconductor laser whose emitted beams can be dynamically controlled by varying their relative lattice constants.

A recording density of 1.5 Pb m⁻² using heat-assisted magnetic recording in a bit-patterned media is demonstrated. This represents a dramatic improvement in track width and optical efficiency over continuous media, owing largely to advantageous near-field optical effects.

Water condensation from air using intense, ultrashort laser pulses is demonstrated, an approach that could benefit remote sensing and studies in atmospheric science.

All-optical switching energies as small as 0.42 fJ — two orders of magnitude lower than previously reported — are demonstrated in small photonic crystal cavities incorporating InGaAsP. These devices can switch within a few tens of picoseconds, and may therefore have potential for low-power high-density all-optical processing on a chip.

An ultrafast, all-optical spin echo technique is used to increase the decoherence time of a single quantum dot electron spin from nanoseconds to several microseconds. The ratio of decoherence time to gate time exceeds 10⁵, suggesting strong promise for future photonic quantum information processors and repeater networks.

Polaritons in organic semiconductors are highly stable at room temperature, but so far nonlinear emission from these structures has not been demonstrated. Here, polariton lasing at room temperature in an organic microcavity composed of a melt-grown anthracene single crystal sandwiched between two dielectric mirrors is reported.

Room-temperature lasing from metallo-dielectric cavities that are smaller than their emission wavelength in all three dimensions is reported. The cavity consists of an aluminium/silica bi-layer shield that surrounds an InGaAsP disk. The gain threshold of the laser is minimized by optimizing the thickness of the silica layer.

An all-optical spin switch based on exciton–polaritons in a semiconductor microcavity is demonstrated. These results may lead to small and fast spin-based on-chip logic devices.

Evidence that appropriately engineered quantum states outperform both standard and N00N states in the precision of phase estimation — even in the presence of losses and decoherence — is presented. The results show that the strategy for realizing the quantum enhancement of metrology is quite distinct from protecting quantum information encoded in light.

By exploiting the Keldysh scaling — universal wavelength scaling laws in strong-field physics — direct temporal characterization of high-harmonics is demonstrated using sum-frequency-generation cross-correlation frequency-resolved optical gating (SFG XFROG).

A noiseless linear amplifier for quantum states of an optical field is demonstrated. The amplifier is also used to enhance entanglement through a technique known as distillation. Such amplification and distillation may be useful for quantum cloning, metrology and communications.

Researchers overcome the propagation loss of surface-plasmon polaritons, with this demonstration being the first direct gain measurement of propagating plasmons. Low-loss long-range modes of a metal stripe waveguide are amplified by using optically pumped dye molecules in solution as the gain medium. The mode power gain was measured to be 8.55 dB mm⁻¹.