Articles

A terahertz quantum cascade laser and diode mixer are monolithically integrated to form a simple microelectronic terahertz transceiver. The performance of this system — the transmission of a coherent carrier, heterodyne reception of an external signal, frequency locking and tuning — is as efficient as that of discrete component terahertz photonic systems.

Quasi-phase-matching (QPM) has always been thought of as a purely spatial phenomenon. Now, scientists show that QPM can be extended to the temporal domain, introducing temporal and spatiotemporal modulations of the nonlinear susceptibility. This concept paves the way for the manipulation of light through nonlinear interactions, and may have unique applications in nonlinear optics.

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.

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.

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.

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.

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.

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.

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 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.

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.

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.

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.

Ultrabroad-bandwidth radiofrequency pulses that increase data transmission rate and allow multipath tolerance in wireless communications are difficult to generate using chip-based electronics. Now, a chip-scale fully programmable spectral shaper consisting of cascaded multichannel micro-ring resonators is demonstrated as a solution.

Rydberg blockade — the suppression of excitation of more than one Rydberg atom within a blockade volume — has so far been realized using ultracold atoms. Now, scientists show that coherence times of >100 ns are achievable with coherent Rydberg atomic spectroscopy in micrometre-sized thermal vapour cells, making them good candidates for investigating low-dimensional strongly interacting Rydberg gases, constructing quantum gates and building single-photon sources.

The generation of random bit sequences at a data rate of up to 300 Gbit s⁻¹ — a rate many orders of magnitude faster than previously achieved — is realized by exploiting the output of a chaotic semiconductor laser. The randomness of the generated bits is verified by standard statistical tests.

A terahertz wire laser with an unprecedented tuning range of ∼137 GHz has been demonstrated. This scheme relies on bringing dielectric or metallic structures into close proximity with the wire, thus modifying the properties of its guided mode.