Volume 3 Issue 3, March 2009

Powerful lightning strikes pose a significant threat to buildings and people, but imagine if it were possible to control and direct them with a laser beam. Nature Photonics spoke to Jérôme Kasparian, a researcher from the University of Geneva and co-ordinator of the Teramobile project, about the idea.

Photoacoustic imaging, using laser light to stimulate the emission of ultrasonic waves from tissue inside the human body, potentially offers a route to far deeper imaging than possible with conventional optical techniques, reports Duncan Graham-Rowe.

LEDs are receiving great interest as candidates for next-generation lighting because they promise to reduce energy consumption enormously. However, to be a feasible solution their quantum efficiency needs to improve. Now, it seems that the incorporation of photonic crystals may be an answer.

Electrically tunable metamaterials make it possible to create the first solid-state phase modulator operating at terahertz frequencies.

Researchers in South Korea and the Netherlands have demonstrated that the enhancement of the electric field of terahertz radiation inside a nano-slit continues to grow, even when the slit becomes narrower than the skin depth of the material.

The high-resolution imaging of individual colour centres in diamond using stimulated emission depletion microscopy is set to offer new insights into the physics underlying solid-state light emitters.

A transition between strong and weak coupling regimes in a polariton diode microcavity yields optically controlled switching of current. Researchers show bistable cycles for optical powers two to three orders of magnitude less than typical schemes.

By carefully optimizing the properties of a waveguide made from a highly nonlinear glass, Australian researchers have achieved record optical nonlinearity and put it to use in a broadband radiofrequency spectrum analyser. The work could ultimately lead to improved all-optical signal processing.

A system based on a highly nonlinear planar chalcogenide waveguide is demonstrated to be able to perform radio-frequency spectral measurements with a terahertz bandwidth. High bit-rate tests show that the chip-based system is potentially useful for ultrafast signal processing.

Based on a far-field fluorescence-based optical super-resolution scheme – stimulated emission depletion microscopy – scientists resolve densely packed individual fluorescent colour centres inside crystals with a far-field spatial resolution of 5.8 nm without photobleaching. The approach will support future studies of solid-state single-photon sources and quantum optics.

Using a single layer of electrically controlled metamaterial, researchers have achieved active control of the phase of terahertz waves and demonstrated high-speed broadband modulation.

The effect of a tiny gap in a metal substrate on incident terahertz radiation in the regime where the gap's dimensions are smaller than the metal's skin-depth are investigated. The results and theoretical analysis show that the gap acts as a capacitor charged by light-induced currents, and dramatically enhances the local electric field.

Controlling the orientation of the constituent parts of a metamaterial enables the creation of a new family of optical stereoisomer materials that have an electromagnetic response that can be carefully tailored.

Blue light-emitting diodes with a light extraction efficiency of 73% are reported. The InGaN–GaN devices use a photonic-crystal structure for superior optical mode control; their performance has been characterized experimentally and modelled theoretically.

Spatial control of the phase and amplitude of a laser beam is useful for applications ranging from imaging and holography to interferometry and optical tweezers, reports Neil Savage.

It has now been shown that twisting the orientation of layers in a metamaterial provides a new way of tailoring their electromagnetic properties. Nature Photonics spoke to Harald Giessen and Na Liu from the University of Stuttgart about the idea.