Volume 5 Issue 9, September 2011

Scientists in Japan struggled in the aftermath of a catastrophic earthquake, radiation problems and power cuts. Nevertheless, they have now largely recovered from the desperate situation.

Scientists have theoretically proposed that it is possible to pull objects from a far distance towards a light source in the absence of axial optical gradient forces.

Although two-photon absorption in a semiconductor is typically a very weak effect, the rate of absorption increases dramatically when the two photons have very dissimilar wavelengths, enabling applications such as ultrafast optical sampling and room-temperature mid-infrared detection.

Going beyond the conventional approach based on the Faraday effect, scientists have now used acoustic modes optically excited in the core of a photonic crystal fibre to realize a reconfigurable all-optical isolator.

Plasmonics has great potential for enabling energy-efficient, highly integrated optical interconnects. Reducing loss and realizing CMOS-compatible active plasmonic devices are two of the main topics on the current agenda.

Are blue and green vertical-cavity surface-emitting lasers operating at room temperature just around the corner? New gallium-nitride-based vertical-cavity surface-emitting lasers are helping to overcome the intrinsic problem of low conductivities of p layers.

Theoretical analysis suggests that there exists an optical attractive force capable of “pulling” microparticles towards a light source. This backwards force is generated by using interference to optimize the scattering of light in the forwards direction.

Scientists demonstrate a low-cost technique for implementing arbitrarily designed surface morphologies directly into functional zinc oxide films. The researchers achieve conversion efficiencies of 10.1% when applying the films as transparent front electrodes in amorphous silicon solar cells.

Materials that exhibit strong reflectivity of hard X-rays at normal incidence are sought after for components such as hard-X-ray cavities, beamsplitters and delay lines. Here, researchers experimentally demonstrate hard-X-ray reflectivities of more than 99% from diamond crystals at near-normal incidence.

Researchers demonstrate solution-processed light-emitting diodes based on a quantum-dot emissive layer between an organic hole-transport layer and an electron-transport layer of ZnO nanoparticles. The device achieves a luminance of 68,000 cd m⁻² and power efficiencies of up to 8.2 lm W⁻¹.

Scientists experimentally demonstrate a reconfigurable all-optical isolator based on the optical excitation of a gigahertz guided acoustic mode in a micrometre-sized photonic crystal fibre core. The work is expected to benefit advanced optical communications and all-optical signal-processing systems.

Researchers show that dispersed functionalized graphene can exhibit broadband nonlinear optical absorption at fluences well below the damage threshold. An optical energy-limiting onset benchmark of 10 mJ cm⁻² at a linear transmittance of 70% was obtained for nanosecond visible and near-infrared pulses. The findings shed light on the formation of practical thin films with broadband optical limiting characteristics.

Researchers use extremely non-degenerate photon pairs to achieve two-photon absorption at levels 100-1,000 times that of degenerate two-photon absorption in direct-gap semiconductors. The technique enables the gated detection of sub-bandgap and sub-100-pJ mid-infrared radiation using large-bandgap detectors at room temperature.

Optically pulling a particle towards a light source may be counterintuitive, but it is not impossible. Jack Ng tells Nature Photonics how this force can be achieved.