Articles in 2009

Researchers at Stanford University and the Max Planck Institute for Polymer Research have demonstrated fluorescence enhancements ten times greater than previously demonstrated, by placing single fluorophores in an optical bowtie nano-antenna.

Visual encryption, manipulation of terahertz waves and the improved surface-treatment of GaN crystals were all topics of discussion at this year's JSAP meeting in Toyama, Japan.

Hyperspectral imaging, traditionally used for airborne remote sensing, is now becoming a valuable tool for in-line inspection and quality control.

Digital holographic microscopy's ability to reconstruct three-dimensional surface topography from a single measurement without the need for any scanning makes it extremely robust and immune to vibrations. Its applications range from bioimaging through to analysing micro-electromechanical systems devices and quality-assurance tasks.

The discovery that the eye of a particular mantis shrimp has an achromatic quarter-waveplate that is superior to modern-day devices could be a source of inspiration to those designing optical components. Nature Photonics spoke to Nicholas Roberts, one of the researchers involved in the study.

Adding electron-withdrawing groups to the backbone of the polymer PBDTTT is shown to increase the open-circuit voltage of photovoltaic cells, resulting in a polymer solar-cell that has a certified power-conversion efficiency of 6.77%.

It is now possible to acoustically control the transfer of electrons and holes between a quantum well and a quantum dot by exploiting the moving piezoelectric potential modulation induced by an acoustic phonon. The effect has been used to demonstrate a high-frequency single-photon source with tunable emission energy, by acoustically transferring carriers to selected quantum dots.

A natural quarter-wave retarder in the eye of a stomatopod is demonstrated to have an achromaticity in the visible wavelength regime that outperforms existing designs of synthetic optical retarders. The performance is shown to be due to compensatory birefringent effects that eliminate wavelength dependence, resulting in an almost constant retardation at 450–700 nm.

So-called photonic-crystal-excitonic-lattice polaritons can be observed by coupling excitons and Bloch waves in a periodic arrangement of GaAs/AlGaAs quantum wells. The effect can be tuned by using an electric field. These hybrid states may allow slow-light-enhanced nonlinear effects and enable observation of macroscopic coherence phenomena in solid-state systems.

A 1,340-fold increase in single-molecule fluorescence has been observed from a lithographically fabricated gold bowtie nanoantenna — approximately an order of magnitude greater than that achieved in previous reports on such structures. The improvement results from an estimated ninefold increase in quantum efficiency, caused by enhanced absorption and an increased radiative emission rate.

Single SiC whiskers can be made into infrared emitters by thermal excitation. The broadband thermal emission is coupled to the electromagnetic resonances of the whisker, allowing relatively narrowband emission at infrared frequencies. The emission frequency can be tuned by adjusting the size of the whiskers.

The news that spherical droplets of a liquid crystal can function as whispering-gallery-mode microresonators with an unprecedented width of wavelength tunability could be good news for fabricating new kinds of sensors and lasers.

Analysis of the spectral content of light is important in countless applications, ranging from biomedicine to material analysis and product quality control, reports Neil Savage.

Strain gauges that change colour when stressed, bright backlight-free displays and highly sensitive biological sensors are all potential applications of tunable photonic crystal materials, reports Duncan Graham-Rowe.

The use of cascaded nonlinear silicon waveguides that function as 'time lenses' is providing new opportunities for generating and measuring ultrafast optical waveforms.