Volume 5 Issue 11, November 2011

Attosecond electron wave packets produced during the interaction between strong optical fields and atoms provide rich information about the quantum states of their parent ions, in the form of scattered electrons or emitted photons that have attosecond temporal resolution and ångström spatial resolution.

The use of a custom-shaped hollow metallic cone can dramatically improve the efficiency of converting infrared to extreme-ultraviolet light, bringing the prospect of a compact laser-like source for next-generation lithography and imaging in the biological 'water window' a step closer to reality.

Could holes in semiconductor quantum dots be a more appealing alternative to electrons for realizing stable and scalable solid-state spin qubits for quantum information processing? The latest findings detailing two coupled dots and improved coherence times suggest that the answer may be yes.

Although constructing a perfect invisibility cloak is beyond our present capabilities, the more modest goal of achieving deception now seems to be a realistic alternative.

By combining the benefits of multidimensional spectroscopy with photoemission electron microscopy, scientists in Germany have successfully mapped the coherence lifetimes of plasmons in silver with nanoscale spatial resolution and femtosecond temporal resolution.

The detection of ultralow concentrations of molecules using nanoscale optical sensors is hindered by the difficulty in bringing the two into contact, where diffusion acts on impractical timescales. Fortunately, introducing plasmonic structures to super-hydrophobic surfaces may offer a way around this problem.

Photovoltages generated from semiconducting single-walled carbon nanotubes are often too small for most practical solar-energy-harvesting applications. Here, researchers demonstrate that virtual contacts can be used to multiply photovoltages from around 0.2 V to 1.0 V.

Researchers use plasmonic nanofocusing of near-infrared pulses in metallic tapered gap waveguides to generate ultrashort extreme-ultraviolet pulses. They calculate that the electromagnetic field intensity is around 350 times higher than that of a reference untapered waveguide, allowing harmonics up to the 43rd to be realized at a modest incident intensity of ∼10¹¹ W cm⁻².

Surface-enhanced Raman sensors often rely on random chance for molecules to come near optical hotspots. Here, researchers use super-hydrophobic artificial surfaces and evaporation to direct molecules to plasmonic light-focusing structures. Molecules can be localized and detected even at attomolar concentrations.

Researchers demonstrate two-stage laser stabilization based on a combination of Fabry–Pérot and spectral-hole burning techniques. The laser was first pre-stabilized using Fabry–Pérot cavities and then modulated to address a spectral-hole pattern in Eu³⁺:Y₂SiO₅. Taking advantage of the low sensitivity of the spectral holes to environmental perturbations, the researchers obtained a fractional frequency stability of 6 × 10⁻¹⁶

Re-absorption losses in luminescent solar concentrators cause concentration performances to be around ten times less than the ideal value. Researchers have now reduced re-absorption by forcing the emission in one region to be off-resonant with the other regions, achieving a two-fold enhancement in concentration performance over conventional devices.

Researchers demonstrate fast, single-qubit gates using a sequence of 13 ps pulses. Two vertically stacked InAs/GaAs quantum dots were coupled through coherent tunnelling and charged with controlled numbers of holes. The interaction between hole spins was investigated by Ramsey fringe experiments, showing a tunable interaction range of tens of gigahertz.

Luminescent solar concentrators have long been hampered by reabsorption losses. Nature Photonics spoke to Noel Giebink about how to circumvent this effect.