Spectroscopy

Photonics does not just mean optics performed at the chip-scale or below, at least not by the definition we use at Nature Photonics. Our September issue showcases research from some large-scale facilities, demonstrating the broad range of topics that the journal considers.

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.

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.

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.

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.

Table-top laser-driven plasma accelerators have the potential advantages of being ultracompact and powerful. Electron beams can be created by irradiating gas jets with intense laser light, however, until now it has proved difficult to achieve stable, high-energy beams. Jongmin Lee and colleagues report the first generation of stable gigaelectronvolt-class electron beams using a laser-based accelerator, and make an important step along the road to future particle accelerators.

The pollutant emissions and high-energy consumption of combustion engines using conventional spark plugs have long been serious environmental problems. Now, it has been demonstrated that lasers can provide a feasible green alternative. Duncan Graham-Rowe reports.

Researchers at Hamamatsu report an indium-free laser diode operating at 342 nm, the shortest wavelength so far for an electrically pumped semiconductor laser diode.

Necessity is the mother of invention. Lasing in the extreme UV from a prototype compact free-electron-laser design is reported, continuing the push towards X-ray wavelengths.

Laser beams have an intrinsic spread. Normally this spread is overcome using lenses or curved mirrors to focus the light, but this typically involves meticulous optical alignment. Researchers have now shown that a surface-plasmon technique can reduce the beam spread.

Laser-based accelerator technology has been given a boost thanks to researchers based in Korea, Japan and the USA. Their latest research could lead the way towards compact accelerators that can deliver brilliant electron and X-ray beams.

Supercontinua — bright broadband light pulses — are helping a plethora of applications in imaging, sensing and defence. Nature Photonics reports from Sydney, Australia.

Introducing coded apertures to X-ray laser holography paves a route to efficient imaging at the nanoscale.

Previously regarded as a laboratory method for the characterization of metal alloys, laser-induced breakdown spectroscopy is now showing great potential for field-based environmental monitoring and biohazard analysis.

Terahertz technology seems set to become important in security screening and the pharmaceutical industry.

Noise reduction, integrated spectrometry and microscopy apparatus, and more.

Attosecond spectroscopy promises real-time observation of the motion of electrons inside atoms. Nadya Anscombe talks to Ferenc Krausz from the Max-Planck Institute of Quantum Optics and the Ludwig-Maximilians-University of Munich in Germany about the technology.

Particle accelerators are one of the most remarkable pieces of apparatus to come out of twentieth century science. Nature Photonics spoke to Nasr Hafz who, with the help of colleagues, is working towards more compact and thus more affordable accelerators based on lasers.