Articles in 2008

Liquid-crystal displays are hugely successful in today's world, but their back-light transmission efficiency is relatively small. Nature Photonics spoke to Anna Pyayt, who, with colleagues at Microsoft, has devised a display approach that could offer improved light efficiency at lower cost.

A round-up of recent papers in the field of photonics published by the physical sciences division of the Nature Publishing Group.

Slow-light effects in ultracold atom clouds known as Bose–Einstein condensates offer rich opportunities for storing and processing optical signals.

X-ray Fourier transform holography using free-electron lasers has the potential to enable nanoscale imaging on the timescale of atomic motion. A technique that dramatically increases the efficiency of this technique could move us a step towards such imaging.

The unique properties of wide-bandwidth and dispersion-free propagation in photonic-crystal devices have made them a good candidate for slow-light generation. This article gives the background theory of slow light, as well as an overview of recent experimental demonstrations based on photonic-band engineering.

This article reviews different approaches for slow- and fast-light generation in optical fibres at telecommunication wavelengths, with emphasis on the stimulated–Brillouin–scattering approach — a relatively active area in optical–fibre–based control of slow and fast light.

Nanfang Yu and colleagues show that plasmonics can be used to reduce the spread of laser beams. They demonstrate their technique using a quantum cascade laser, and show that by defining a metallic subwavelength slit and grating onto the facet of the laser, a beam divergence of 2.4 degrees can be achieved. The technique can potentially be used to collimate the beams from a variety of different lasers.

Short-wavelength UV laser diodes are required for applications ranging from sensing, data storage and materials processing. Here, an electrically driven semiconductor laser that operates at 342.3 nm, the shortest wavelength so far, is reported. The device emits milliwatt-scale powers at room temperature when driven by pulsed current.

Frequency mixing the fundamental-and second-harmonic fields of an ultrafast laser in any one of a number of materials can generate radiation at terahertz frequencies. A better understanding of this process leads to a brighter source of light at these very useful wavelengths.

Free-electron lasers can produce powerful pulses of radiation at very short wavelengths, even in the hard-X-ray region. In general, however, they comprise facilities several kilometres in length. A 55-m-long laser could open up the technology to a broader range of researchers.

Several technologies have been invented as alternatives to the LCD, which transmits only a small portion of the backlight. Now researchers have come up with a display involving a telescopic pixel design, which can transmit 36% of the backlight. The eventual result could be large, bright displays that offer higher contrast at a low cost.

Xiang Zhang and colleagues from the University of California, Berkeley, propose a new approach for confining light on scales much smaller than the wavelength of light. Using hybrid waveguides that incorporate dielectric and plasmonic waveguiding techniques, they are able to confine surface plasmon polaritons very strongly over large distances. The advance could lead to truly nanoscale plasmonics and photonics.

Before the practical implementation of quantum information schemes, there is a need to reduce loss, both in terms of photons and the information they carry. A robust scheme now experimentally demonstrated tackles this problem using so-called decoherence-free subspace.

Extracting light from organic LEDs is difficult owing to the refractive index of the materials used, and the output efficiency is typically limited to around 15–20%. By embedding a grid with a low refractive index into the organic layers and using a microlens array researchers have now managed to increase this figure to 34%, representing an improvement by factor of 2.3 over a conventional device.

Photonics research features heavily in the 2008 Prince of Asturias Awards, where its role in benefiting the environment and combating poverty is celebrated.

A tiny GeSi electro-absorption modulator with energy consumption at the femtojoule-per-bit level represents a step towards bringing photonics ever closer to computer chips.

The ability of a customized avalanche-photodiode detector to distinguish the exact number of photons that it receives will simplify the tools required to perform reliable experiments in quantum optics.