Research articles

A graphene-based photodetector with unprecedented photoresponsivity and the ability to perform error-free detection of 10 Gbit s⁻¹s data streams is demonstrated. The results suggest that graphene-based photonic devices have a bright future in telecommunications and other optical applications.

Scientists report a mode-locking regime of an erbium-doped fibre laser in which the laser pulse evolves as a similariton in the gain segment of the cavity and transforms into a soliton in the rest of the cavity. The findings constitute the first observation of amplifier similaritons in a laser cavity and are likely to be applicable to various other nonlinear systems.

By exploiting stochastic resonance — in which nonlinear coupling allows signals to grow at the expense of noise — scientists show that they can recover noise-hidden images propagating in a self-focusing medium. The findings pave the way for a variety of nonlinear instability-driven imaging techniques.

Precise spatial characterization of the origin of light emission from organic light-emitting diodes is important for improving the design of future devices and gaining valuable insight into their operation. Here, a characterization scheme that achieves this task with a spatial resolution better than 5 nm is reported.

A Yagi–Uda directional antenna — the work horse of radiofrequency communications for more than 60 years — has now been demonstrated at visible wavelengths. An array of appropriately tuned nanoparticles replicate the reflecting and directing elements of the original design. Directional control of radiation from the nano-optical Yagi–Uda antenna was experimentally shown.

Entangled photons are efficiently generated from highly symmetric, site-controlled InGaAs/GaAs quantum dots grown in inverted pyramids. Fine-structure splitting of the intermediate exciton level is suppressed without the application of electric, magnetic or strain fields. Polarization entanglement is demonstrated by measurements of the two-photon density matrix and the confirmation of several entanglement criteria.

Quantum memories for storing and releasing photons are required for quantum computers and quantum communications. So far, their operational bandwidths have limited data-rates to megahertz. Researchers now demonstrate coherent storage and retrieval of subnanosecond low-intensity light pulses with spectral bandwidths exceeding 1 GHz.

Sub-shot-noise imaging using spatial quantum correlations between parametric down-conversion light beams is demonstrated. The scheme exhibits a larger signal-to-noise ratio than is possible through classical imaging methods.

A measurement scheme that is capable of recording the amplitude and phase of arbitrary shaped optical waveforms with a bandwidth of up to 160 GHz is presented. The approach is compatible with integration on a silicon photonic chip and could aid the study of transient ultrafast phenomena.

Organic light-emitting diodes featuring layers with a spontaneously formed buckled geometry are demonstrated to offer at least a twofold improvement in light extraction efficiency across the entire visible spectrum.

Light is scattered out of a focusing beam when an inhomogeneous medium is placed between the lens and the focal plane. Now, scientists experimentally demonstrate that scattering can be exploited to improve, rather than deteriorate, the focusing resolution of a lens by using wavefront shaping to compensate for scattering.

Tailoring of arbitrary single-mode states of travelling light up to the two-photon level is proposed and demonstrated. The desired state is remotely prepared in the signal channel of spontaneous parametric down-conversion by means of conditional measurements on the idler channel.

Distillation of entangled photons is essential for applications such as long-distance quantum communication and high-fidelity quantum teleportation. Distillation from Gaussian input states is experimentally realized, resulting in a large gain in entanglement.

Nanocavity optomechanical systems can exhibit strong dynamical back-action between mechanical motion and the cavity light field. Here, optical control of mechanical motion within two different nanocavity structures is demonstrated. A form of optically controlled mechanical transparency is also demonstrated, which is analogous to electromagnetically induced transparency.

Fine control over the material structure within a volume gives rise to new physical phenomena and more freedom for designing spatial, spectral and temporal functions. A three-dimensional scattering approach to the design of aperiodic volume optical elements is presented, expanding the traditional capabilities of volume holography, photonic crystals and diffractive optics.

The combination of distributed Rayleigh back-scatter and Raman gain in an optical fibre yields an open cavity, mirror-less fibre laser that offers stable operation at the telecommunications wavelength of 1.5 µm.

The lack of effcient solid-state sources of single photons is impeding the further development of many fields including quantum communication, quantum information processing and metrology. Using an InAs quantum dot embedded in a GaAs photonic nanowire with carefully tailored ends, researchers demonstrate a record single-photon source effciency of 0.72 under optical pumping.

The first enhancement cavity for femtosecond ultraviolet pulses is demonstrated. More than 7 W of average ultraviolet power at an 81 MHz repetition rate, available to pump a nonlinear crystal inside the cavity, is exploited in an implementation of a powerful source for high-rate experiments with entangled multiphoton states.

Scientists demonstrate that a single 7.5-μm-diameter microdisk laser coupled to a silicon-on-insulator wire waveguide can work as an all-optical flip-flop memory. Under a continuous bias of 3.5 mA, flip-flop operation is demonstrated using optical triggering pulses of 1.8 fJ and with a switching time of 60 ps. This device is attractive for on-chip all-optical signal buffering, switching, and processing.

Researchers have constructed a terahertz quantum cascade laser using quasi-periodic distributed feedback gratings based on the Fibonacci sequence. Features that go beyond traditional distributed feedback lasers are demonstrated, such as directional output independent of the emission frequency and multicolour operation.