Terahertz

As a desire to make a new regular feature on this site, I’m launching the first Photonics Briefs, featuring new articles, research, and news on the field of photonics. For the first couple issues most of my news will likely come from Nature Photonics, although in the future I’ll try to look around a bit more. So hopefully every Sunday from now on you should be able to see a new edition of Photonics Briefs.

First up, the cover issue of Nature Photonics this week is on replacing internal combustion engine spark plugs with lasers! The idea is to focus an intense nanosecond pulse into the chamber where the gas and air mix. The intense laser intensity causes air to ionize and a spark is created in the chamber. The authors claim that this is not as unrealistic as you might think. They cite several advantages to using lasers over traditional spark plugs: increased efficiencies, reduced NO_x pollutants, and the ability to use leaner (more air to fuel) mixes. GE, Ford and Toyota are supposedly already looking into the idea.

• Duncan Graham-Rowe & Rachel Won, “Lasers for engine ignition”, Nature Photonics 2, 515-517 (2008).

Next up, there’s a feature interview with Nasr Hafz, who works at the Advanced Photonics Research Institute in Korea. There he and his colleagues use lasers to accelerate electrons over the span of a centimetre to speeds which used to take several meters of space. The basic idea is that a laser beam enters a plasma (an electrically charged gas) which causes the negative and positive charges to split apart – as the pulse leaves the plasma the electrons accelerate across the gap and a couple are extracted for relativistic electron experiments. The key advantage here is that a typical lab room can perform experiments that used to require entire buildings. Their group is already achieving 1 GeV energies. To put this in perspective, many synchrotrons are able to reach around this level (the new LHC is 14 TeV, or 14,000 times more energetic). This puts a lot of power in a very small space.

• Interview with Nasr Hafz, Nature Photonics, 2, 580 (2008).

Finally, the technology focus (on spectroscopy) features an interview with Ferenc Krausz from the Max-Planck Institute of Quantum Optics and the Ludwig-Maximilians-University of Munich in Germany on attosecond laser technology (which was first discovered in Canada at the National Research Council in Ottawa). Attosecond lasers are the next frontier after femtosecond lasers, and are now the shortest pulses in existence. An attosecond is 10^-18 seconds or one billionth of one billionth of a second. On this time scale some really cool physics can be observed. This is the time scale of the orbit of an electron around an atom. This is also about the time it takes an light to travel the length of a few atoms or small molecules. So far the coolest thing I’ve heard accomplished with attosecond spectroscopy was the imaging of the wavefunction of a nitrogen molecule (usually we can only talk about the probability or magnitude squared of the wavefunction, but Paul Corkum’s group in Ottawa claims to have actually measure the wavefunction). This is a really exciting field in photonics, and a lot cool stuff is likely to come out in the near future from these groups.

• “Attosecond Science”, Nature Photonics, 2, 548 (2008).

So watch next Sunday for my next photonics briefs. Also, feel free to suggest any updates I should include in this feature.

[tags]science, photonics, attosecond, laser ignition, particle accelerator[/tags]