Volume 7 Issue 1, January 2013

In three-dimensional disordered media, light localization can occur when the disorder is above a certain threshold. Researchers now report experimental evidence of this transition from light diffusion to trapping.

Combining concepts from Doppler-free spectroscopy, coherent quantum control and frequency comb spectroscopy leads to new opportunities for the precision excitation of atomic species with high resolution, both spectrally and spatially.

Light is an excellent tool for making precise measurements of objects, but can sometimes alter or damage a sensitive sample. Researchers have now shown that entanglement and quantum-correlated light can be used to help alleviate this problem.

Attosecond photonics has contributed to a wide range of important scientific and technological breakthroughs. The challenges now are to realize high-energy attosecond sources and to simplify attosecond technologies for widespread use.

This Review article summarizes the key advantages of using quantum dots (QDs) as luminophores in light-emitting devices (LEDs) and outlines the operating mechanisms of four types of QD-LED. The key scientific and technological challenges facing QD-LED commercialization are identified, together with on-going strategies to overcome these challenges.

Attracting objects with optical beams may seem like science fiction, but various schemes already do this, albeit with some caveats and limitations. The most recent progress in this emerging field is reviewed, with particular emphasis on manipulation of small objects by optically induced 'negative forces'.

Researchers report the entanglement-enhanced measurement of a delicate material system, in which they non-destructively probe an ⁸⁵Rb atomic spin ensemble by near-resonant Faraday rotation. They use narrowband, atom-resonant ‘NOON’ states to beat the standard quantum limit of sensitivity by more than five standard deviations, both on a per-photon and a per-damage basis.

A parallel implementation of multifocal multiphoton modulation microscopy allows simultaneous phosphorescent lifetime and intensity imaging in vivo at speeds 100 times faster than conventional configurations. Three-dimensional imaging of a phosphorescent quenching dye is also presented.

Coherent control is a powerful tool for controlling light–matter interactions in time and frequency. Now, scientists show that counter-propagating broadband pulses can be used to generate fully controlled spatial excitation patterns. This spatial control approach also reduces decoherence, providing a high-frequency resolution similar to that of an optical frequency comb.

Researchers focus 10 keV X-ray free-electron laser radiation to an area of 0.95 µm × 1.20 µm with near-100%-efficiency using reflective optics. This approach increases the fluence by a factor of 40,000 and provides a power density of 6 × 10¹⁷ W cm⁻².

Experimental demonstration of Anderson localization in three dimensions is a challenging task. Here researchers present a direct and absorption-independent measure of the localization length and evidence for a localization transition in three dimensions.

Scientists report that the photovoltaic effect and a photo-induced bolometric effect, rather than thermoelectric effects, dominate the photoresponse during a classic photoconductivity experiment in biased graphene. The findings shed light on the hot-electron-driven photoresponse in graphene and its energy loss pathway via phonons.

Chaotic behaviour is observed in the polarization of the output from a vertical-cavity surface emitting laser without the need for any external stimulus or feedback. The origin is nonlinear coupling between two elliptically polarized modes within the device.

Random lasing in the presence of nonlinearities and disordered gain media is still poorly understood. Researchers now present a semiclassical theory for multimode random lasing in the strongly scattering regime. They show that Anderson localization — a wave-interference effect — is not affected by the presence of nonlinearities, but instead suppresses interactions between simultaneously lasing modes.

Researchers demonstrate that Bell's measure — a commonly used test of quantum nonlocality — can be used in classical optical schemes to separate incoherence associated with statistical fluctuations from incoherence based on correlation. This technique may be useful for quantum information applications such as classical optical coherence theory and optical signal processing.

Optical coherence theory has a long and proud tradition. Nature Photonics spoke to Ayman Abouraddy and Kumel Kagalwala to learn about their recent work, which may reshape this established field.