tEChnology UV lAsERs
Extreme
Rob Coppinger investigates the applications being opened up by new sources of extreme UV
xtreme ultraviolet (EUV) tends to be associated with lithography for semiconductor chips. But photonics in the extreme ultraviolet has a
much more diverse and interesting range of applications than chip lithography. This is, perhaps, just as well because no microchip has yet gone into production using this technology. Scientists are already looking to extend the
wavelength range down through what is called the ‘water window’ – wavelengths between 2nm and 4nm – towards the soft x-ray region. At these sorts of wavelengths, researchers are finding new applications for EUV, also known as XUV, from cutting operations, to spectroscopy, imaging of biological samples, to data storage. In developing novel materials for use in ultra-high speed data storage, scientists need to be able to analyse what is going on inside the materials. The ultra high-speed data storage would use the laser to switch electrons’ state between what would represent a one and what would represent a zero. Extreme UV is of interest
www.electrooptics.com
is now mainstream E
as a research tool, because it can examine events occurring at very short timescales. Professor John Collier, director of the central laser facility at UK’s Science and Technology Facilities Council (STFC), points out that the beams are ‘getting down into a few nanometres in wavelength space and it is also extremely short, just a few tens of femtoseconds long. That then goes into an experimental station and we can use that pulse of light as a way of diagnosing what is going on inside materials.’
‘EUV opens the way for new devices and
technologies such as ultra high-speed data storage. Imagine you could find a way of switching magnetic systems on a femtosecond timescale. That would have a very big impact on data storage,’ Collier explaines. Collier’s facility uses high harmonic
generation to generate very high frequency (and hence very short wavelength) short-pulse radiation by multiplying up the frequency of an initial, longer wavelength laser. The process starts with a conventional titanium sapphire laser that
december 2011/janUary 2012 l ElECtRo optiCs 25 ➤
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