SASER is the acoustic analog of a laser

[Mk]

http://www.aip.org/pnu/2006/split/779-1.html

Sound amplification by stimulated emission of raciation, or SASER, is the acoustic analog of a laser. Instead of a feedback-built potent wave of electromagnetic radiation, a saser would deliver a potent ultrasound wave.
[...]
In these wells, really just carefully confined planar regions, electrons can be excited by parcels of ultrasound, which typically possesses millielectronvolts of energy, equivalent to a frequency of 0.1-1 terahertz. And just as coherent light can build up in a laser by the concerted, stimulated emission of light from a lot of atoms, so in a saser coherent sound can build up by the concerted emission of phonons from a lot of quantum wells in the superlattice.

In lasers the light buildup is maintained by a reflective optical cavity. In the U.K.-Ukraine saser, the acoustic buildup is maintained by an artful spacing of the lattice layer thicknesses in such a way that the layers act as an acoustic mirror (see figure at Physics News Graphics).

Eventually the sound wave emerges from the device at a narrow angular range, as do laser pulses. The monoenergetic nature of the acoustic emission, however, has not yet been fully probed. The researchers believe their saser is the first to reach the terahertz frequency range while using also modest electrical power input. Terahertz coherent sound is itself a relatively new field of research. Essentially ultrasound with wavelengths measured in nanometers, terahertz acoustical devices might be used in modulating light waves in optoelectronic devices.

Diagram: http://aip.org/png/2006/260.htm
Paper: http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=PRLTAO000096000021215504000001&idtype=cvips&gifs=yes

 

[Irresistible_Force]

Like the sound weapons in Dune?

 

[Farsight]

Interesting, MK. Do you know if this wikipedia write-up of phonons is reliable?

http://en.wikipedia.org/wiki/Phonon

 

[Kazza_765]

Like the sound weapons in Dune?

Arghh. Read the book, the movie was all wrong.

 

[Mech_Engineer]

This reminds me of a prototype LTL weapon I read about in Popular Science (I think is was PopSci anyway), a "microwave emitter" gun that would shoot out a beam that produces incredible pain to whoever is in its path, but leaves no permanent effects. The author of the article stood in front of it and could only stand there for a second, maybe two. I think they were trying to mount it on a Humvee, but power was an issue... when isn't power an issue with these new weapons?

A great way for riot dispersal...

 

[Danger]

Mech, 'How Stuff Works' also has an article about the microwave unit, but it's listed as a 'pain gun'.

 

[Mech_Engineer]

Yup, looks like the artice was in PopSci in 2003...

http://www.popsci.com/popsci/science/40b7359b9fa84010vgnvcm1000004eecbccdrcrd.html

 

[J77]

I was going to ask what 'raciation' was, but, looking at the PRL, it's a typo (c -> d)

 

[eeka chu]

Sounds (meh meh meh meh meeeeh) a bit like some of the research I heard about into cooling and heating things using sound. Seem to be quite a cool () topic at the moment.

Some guys where trying to build a fridge using a super duper loud speaker. I think the goal may have been to get it to reach cryogenic temperatures such that it could be used for superconducting equipment - think of that experiment where you dip one end of a tube into cryogen and it acoustically sings due to the mechanical changes brought about by the extreme temperature gradient within the tube.

Loads of experiments can benefit from being able to achieve cryogenic temperatures in a tiny space, specially ones that end up in orbit.

I've seen a tiny cryogenic solid state fridge that's about the size of your thumb. It's partially cooled by nitrogen I think, then pumps the rest of the heat out down towards helium temperatures... I think. Anyway, it was tiny and cool looking, and roughly related to my ultra high volume fridge comment.

I too was about to ask what raciation is.

Whilst on the topic of lasers, does anyone know what the highest energy laser is at the moment? I know deep blue / UV lasers are commercially available now thanks to Shuji Nakamura, and that the problem with x / gamma wavelengths is the energy transition required and finding something that can exist in a metastable state at such extremes (I heard the word 'isomer' being coined for such laser mediums and that they'd rely on changes in the nucleus as opposed to the electron shell). What about the other direction, are there any lasers that work in the long radiowave spectrum? Can't seem to find much information on the net about these two extremes. Loads for in between, obviously.