Volume 3 Issue 2, February 2009

While many areas of photonics are being hit hard by the global recession and credit-crunch, others such as solar energy generation and solid-state lighting seem to be continuing to flourish.

Accurate and efficient testing is essential for ensuring the quality and safety of the food we eat. Whereas most analysis methods are destructive, Duncan Graham-Rowe reports that optical techniques are not only non-invasive but in some cases can also assess nutritional content.

Practical low-loss metamaterials at optical frequencies may soon be realized thanks to optical parametric amplification that uses backwards propagation of a signal beam in negative-index metamaterials. Surprisingly, increasing losses at the idler frequency leads to broadband transparency or amplification at the signal frequency.

Storing a light pulse in a vapour is by now a standard laboratory technique. For such optical memory to become truly practical, however, the fidelity of the technique has to be improved. Combining light storage with nonlinear wave mixing may offer a way forwards.

For integrated photonics to take off, light signals zooming around optical chips must be successfully isolated from one another. Scientists at Stanford University have now designed a miniature one-way valve for light that uses photonic transitions and is potentially compatible with silicon-chip CMOS fabrication processes.

The use of fluorescent tagging and nanoscale waveguides looks set to make real-time DNA sequencing a realistic proposition. Commercial devices based on nanophotonics are expected in 2010.

A spectral decomposition of the fluorescence emission from labelled receptors within cells, together with a simple but accurate data analysis of their mutual Förster resonant energy transfer, can provide high-resolution real-time imaging of the fate of intracellular proteins.

By using an optical frequency comb as a light source for Fourier transform spectroscopy, scientists show that well-resolved absorption and dispersion spectra can be recorded simultaneously, providing sensitive detection of multiple molecular species over a broad spectral window.

The year 2009 marks the tenth anniversary of the first report of white-light supercontinuum generation in photonic crystal fibre. This result had a tremendous impact on the field of nonlinear fibre optics and continues to open up new horizons in photonic science. Here we provide a concise and critical summary of the current state of nonlinear optics in photonic crystal fibre, identifying some of the most important and interesting recent developments in the field. We also discuss several emerging research directions and point out links with other areas of physics that are now becoming apparent.

The realization of a chip-based, broadband optical isolator is of considerable interest for integrated photonics. To date, no technique has been shown to be able to do this using materials and processes that are CMOS-compatible. Now, scientists propose that the use of direction-dependent photonic mode transitions in silicon nanophotonic structures could be the solution.

The tiny phase changes introduced by nonlinear optics performed at the single-photon level is reported in a photonic crystal fibre with carefully designed nonlinear and dispersion properties. The approach may prove useful in future quantum information processing schemes.

By using an optical frequency comb as the light source for Fourier transform spectroscopy, scientists show that well-resolved broadband absorption and dispersion spectra can be recorded in a single experiment, providing sensitive detection of multiple molecular species over a broad spectral window.

The coherent storage and retrieval of a four-wave-mixing normal mode in a hot atomic rubidium vapour may prove to be useful for future information processing schemes.

The combination of spectrally resolved two-photon microscopy, fluorescent tags and appropriate theory makes it possible to determine the complex size, configuration and spatial distribution of proteins in single living cells. The findings made could lead to ways of tracking the cellular dynamics of individual molecular complexes.

The emergence of convenient sources of broadband light spanning the visible and near-infrared is proving increasingly useful for applications involving spectroscopy, imaging and metrology, reports Neil Savage.

Nature Photonics spoke to Zongfu Yu and Shanhui Fan from Stanford University about their proposed 'one-way valve for light' that suits integration on a photonic silicon chip.