Volume 6 Issue 8, August 2012

A single sheet of graphene dramatically changes the nonlinear response of a silicon photonic crystal, enabling ultralow-power optical bistability, self-induced regenerative oscillation and coherent four-wave mixing.

Advances in electron optics and X-ray detection are opening up the periodic table to one of the ultimate goals of microanalysis — single-atom spectroscopy.

The world's second hard-X-ray free-electron laser has now been commissioned in Japan. The facility's compact accelerator and short-period undulator not only minimize space and cost but also ensure excellent output stability.

The reciprocity of light pulse propagation in a disordered photonic structure can be 'switched off' by creating a local, ultrafast nonlinearity.

Over the past five decades, breakthroughs in device design and advances in material and growth technologies have transformed semiconductor lasers from laboratory curiosities into practical devices with real-world applications.

Hydrogen from solar-driven water splitting has the potential to provide clean energy. Current progress towards artificial photosynthetic devices is reviewed, with particular focus on visible light active nanostructures. A vision for a future sustainable hydrogen fuel community based on artificial photosynthesis is outlined.

Researchers demonstrate all-optical wavelength conversion based on a resonant nonlinear process within a terahertz quantum cascade laser. The wavelength of the pump beam (812 nm) corresponds to the interband transitions of the laser. The researchers measured a power-conversion efficiency of 0.13% in the range of 812–818 nm, which is the highest value obtained for such a device.

Researchers provide experimental evidence of intrinsic linewidths approaching the quantum limit in a GaAs/AlGaAs quantum cascade laser emitting at 2.5 THz. Despite the expected dominant broadening effect induced by thermal photons, the measured intrinsic linewidth is 90 Hz — even narrower than that of a semiconductor laser working at significantly shorter wavelengths.

The fabrication of nanoscale p–n junctions from colloidal nanocrystals and quantum dots provides a new architecture for efficient, solution-processed solar cells.

By constructing a thermal emission control device based on a multiple-quantum-well layer embedded in a two-dimensional photonic crystal, researchers demonstrate that they can convert a broadband thermal emission spectrum into a narrowband spectrum with minimal loss of energy.

Researchers report sub-ångström fundamental-wavelength lasing at the SPring-8 Angstrom Compact Free-Electron Laser in Japan. The output has a maximum power of more than 10 GW, a pulse duration of 10⁻¹⁴ s and a lasing wavelength of 0.634 Å.

Researchers use energy-dispersive X-ray spectroscopy to detect X-ray emission from a single erbium atom. Although the measured intensities are relatively weak, the work may allow single-atom X-ray spectra to be obtained from other atomic species.

Researchers show that wavefront shaping enables not only real-time widefield imaging through turbid layers with both coherent and incoherent llumination, but also the imaging of objects outside the line-of-sight using light scattered from diffuse walls.

Scientists report the observation of ultralow-power resonant optical bistability, self-induced regenerative oscillations and coherent four-wave mixing in graphene–silicon hybrid optoelectronic devices at cavity recirculating energies of a few femtojoules. The findings indicate the feasibility and versatility of such devices for use in next-generation chip-scale high-speed optical communications, radiofrequency optoelectronics and all-optical signal processing.

Researchers demonstrate an approach for upconverting near-infrared light in solar cells using an organic dye as an antenna for nanoparticles. Increased absorptivity and overall broadening of the upconverter's absorption spectrum enhance the upconversion process by a factor of around 3,300.

Researchers around the world now have access to a second hard-X-ray free-electron laser facility: the SPring-8 Angstrom Compact Free-Electron Laser in Japan. Nature Photonics spoke to Makina Yabashi and Hitoshi Tanaka from the facility about their achievements and plans for the future.