Volume 2 Issue 4, April 2008

Biological processes often involve multimolecular interactions on a nanometre scale or at very large molecular concentrations, making them difficult to visualize. Optical antennas have the potential to become powerful tools for nanobioimaging by enhancing optical fields on this tiny scale.

Although electronic paper that can display monochrome static images has been growing in popularity, the next generation of products will soon be capable of displaying video in full colour. Duncan Graham-Rowe reports.

The use of inorganic charge transport layers has enabled the fabrication of bright, environmentally stable LEDs that are based on electrically pumped colloidal solutions of quantum dots.

Optical antennas are able to concentrate light on a scale much smaller then the wavelength. By using the probe of an atomic force microscope, it is possible to manipulate a so-called bow-tie antenna, thereby tuning its optical response.

Two-photon emission has now been observed from an electrically pumped semiconductor. The process, which involves the simultaneous generation of correlated photons, could have important implications for quantum information technology.

Optical antennas have already been shown to dramatically enhance molecular excitation and emission processes. Now, a compelling new study illustrates how they can redirect the emission of single molecules.

How black is black? An ideally black material would absorb light perfectly at all angles for all wavelengths. Using arrays of carbon nanotubes, researchers based in New York have now engineered a metamaterial that constitutes the darkest material ever made.

Ceramic lasers look poised to make an impact in photonics thanks to the tantalizing possibilities of high output power, ultrashort-pulse generation and cost-effective production.

Interactions between laser and matter are fascinating and have found a wide range of applications. This article gives an overview of the fundamental physical mechanisms in the processing of transparent materials using ultrafast lasers, as well as important emerging applications of the technology.

By scaling down device size, the principles of radio antennas can be used in the optical regime. These optical antennas act as a bridge between optics and electronics, collecting and enhancing light to enable the creation of tiny semiconductor photodetectors.

Optical antennas are able to concentrate light on a scale much smaller then the wavelength. Bow–tie–shape nanostructures are one example. It is now possible to tune the response of such an antenna by precisely moving one half of the bow tie.

Antennas are used to direct the propagation of radio waves. However, this directionality is not so easy to achieve at optical frequencies. Optical antennas that can direct the emission from single fluorescent molecules represent an intriguing route to single-photon sources.

It is possible that when an electron relaxes from an excited state, it generates not one but two photons. Such two–photon emission has been seen in atomic systems, but never in semiconductors, until now. The experimental observation could have intriguing implications for quantum optics.

Silicon photonics is deemed to be the solution for dense on-chip optical networks. Now, by using cascaded silicon microring resonators, scientists demonstrate an ultracompact switch that is insensitive to wavelength and temperature. The switch also has fast error-free operation in multiple 40-Gbit s⁻¹ optical channels and is suitable for scalable networks.

The authors show that metal oxide and colloidal quantum dots can be combined to fabricate monochrome LEDs with a brightness that matches that of the best organic-based quantum-dot LEDs, but with the advantage of improved shelf-life robustness. The reported maximum external electroluminescence efficiency is nearly 0.1%, which represents a 100-fold improvement over previously reported structures

The increase in laser-diode sales has had a knock-on effect on activity in the diode-driver market. Neil Savage gives an update of the latest products on offer.

Single-photon emission is a well-explored process. But in recent years interest in two-photon emission has grown. Nature Photonics spoke to Meir Orenstein and Alex Hayat in Israel about their latest work, which reports two-photon emission in a semiconductor.