That means the beam produced is of higher quality than other lasers, is extremely straight (even by the exacting standards of a normal laser beam) and can thus be focused onto a small area.
In addition, since a single electron travelling through the device emits light not once (as in most other lasers), but many times, quantum cascade lasers are powerful: Dr Capasso's group has recently shown that they beat conventional semiconductor lasers by a factor of 20.
Those researchers, who are affiliated with the Austrian Academy of Sciences and other European organizations, used lasers to teleport a photon from one Canary Island to the other.
Sibling semiconductors are used in light-emitting diodes, solid-state lasers and other technologies that generate heat and light far more precisely and efficiently than conventional welders, torches, ovens and bulbs.
You and the enemy ship hang in space (relative to each other, at least), firing lasers, missiles and on occasion boarding parties at each other.
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It is quite possible that technologies being developed for other purposes (such as lasers, which are useful for all sorts of advanced materials processing) will make the process cheaper and easier still.
Or any other molecule: if quantum cascade lasers become really cheap, you might never be in danger of leaving the house with halitosis again.
Mr Hudson said he was unaware of any other air ambulances being targeted by lasers, although he had heard of similar instances involving police helicopters.
Femtosecond lasers can also be used to interact with other materials and generate particle beams for experiments, says Karl Krushelnick, of the University of Michigan.
The harpoon is clearly aimed at capturing the larger objects but many other solutions have been proposed, including the use of lasers to nudge space junk out of the way, or using giant nets and space tugs.
Other researchers, in America and Japan, are also looking at using lasers rather than microwaves to transmit power through the atmosphere.
But using infrared femtosecond lasers with carefully selected wavelengths, a US team targeted viruses and bacteria without harming other cells.
Over the past five decades it has led to the development of the Internet, lasers, global positioning satellites, magnetic resonance imaging, DNA sequencing, and hundreds of other technologies.
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