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A 'salty' source of coherent light

Hemos posted more than 8 years ago | from the new-ways-of-doing-things dept.

Science 26

Roland Piquepaille writes "Coherent light is produced by a beam of photons that all have the same frequency and are all at the same phase. And today lasers are the only form of technology that we know able to create such light. But by sending shock waves inside a humble crystalline material -- kitchen salt -- researchers from Lawrence Livermore National Laboratory (LLNL) have found a new way to produce coherent light for the first time in 50 years -- at least in the terahertz frequency range. This could lead to applications in optical communications, quantum computing or shock diagnostics. Read more for additional details and references about this discovery."

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26 comments

Quantum mechanics shows that all objects are waves (2, Interesting)

Device666 (901563) | more than 8 years ago | (#14481315)

Quantum mechanics shows that all objects are waves and therefore may be > coherent [wikipedia.org] . Quantum coherence is usually not an event which can be macroscopicly be sensed.

Aha! (2, Insightful)

Z0mb1eman (629653) | more than 8 years ago | (#14481619)

We're finally about to discover how to extract sunlight out of cucumbers!

The missing step was pickles!

Re:Aha! (4, Interesting)

j_cavera (758777) | more than 8 years ago | (#14482728)

You may think that funny, but... If you take a humble kosher dill and stick a nail into either end, then run normal 110v AC through said pickle, it will glow with a soft yellow light as the salt in the brine becomes excited. Go ahead an try this at home. For some reason, kosher dills do this best. So given this as prior art, I'd take the laser findings with a grain of ... yeah, whatever. - Jim

Photon Shockwave (2, Interesting)

Merlyn_3k (943281) | more than 8 years ago | (#14481783)

So FTFA they have determined through mathematical modeling (verified by experiments with NaCl) that a piezoelectric crystal can create coherent light from the uniform motion of the atoms when the crystal is deformed by a shockwave.

Makes me wonder if sonic stimulation at the resonant frequency could be an effective low-power LASER equivalent.

Re:Photon Shockwave (2, Interesting)

hhawk (26580) | more than 8 years ago | (#14482140)

If it did, would that mean you could use kenetic energy (gun powder, etc.) to trigger a LASER pulse? Meaning you could create a weapon that didn't need a big electrical plug?

Re:Photon Shockwave (1)

didit (820432) | more than 8 years ago | (#14482289)

would that mean you could use kenetic energy (gun powder, etc.) to trigger a LASER pulse?
That's exactly how shockwaves such as the one studied in this work are created. Concerning the big electrical plug, this hypothetical source of coherent photons is so weak that it would require a light amplifier. This one requires an electrical plug.

Re:Photon Shockwave (0)

Anonymous Coward | more than 8 years ago | (#14483079)

So that's how the sonic screwdriver is powered?

Re:Photon Shockwave (2, Insightful)

didit (820432) | more than 8 years ago | (#14482240)

Actually, I did nor see any experiment in this paper. It only consists in modelling.
Concerning sonic stimulation, I'm not sure it could work, but I suppose it would be even less intense. My main concern is about lifetime. How many shockwaves can a crystal support? Remember that defects in the crystal structure are going to destroy the coherence of the emitted light.

Re:Photon Shockwave (1)

Merlyn_3k (943281) | more than 8 years ago | (#14483644)

Sorry, misread TFA (experimental SIMULATIONS)

Resonant stimulation would likely produce a continual low-intensity beam of coherent light (although these are actually microwave frequencies, not visible light)

Defects in crystal structure should not affect coherence until structural collapse of the crystal, because the coherent photons are only emitted from the small area just behind the shockwave, within approx 50nm (according to the graph from the simulation) which is approx 5 orders of magnitude smaller than the wavelength of the emitted light.

Re:Photon Shockwave (1)

pclminion (145572) | more than 8 years ago | (#14482740)

Makes me wonder if sonic stimulation at the resonant frequency could be an effective low-power LASER equivalent.

Shock waves are not sonic.

Re:Photon Shockwave (2, Interesting)

Merlyn_3k (943281) | more than 8 years ago | (#14483744)

A shockwave is not a sound wave, true.

But a shockwave is a sharp pressure differential, on the order of a sawtooth wave, which in a stationary object would almost have to be created by an explosion. The shockwave propagates through a medium at the same velocity as more conventional compression waves (sound)

A high amplitude sawtooth (or as near as practical) sound wave at the resonant frequency of the medium may be able to mimic the high pressure differential and synchronized atomic motion of a shockwave.

Of course, these are after all piezo crystals we are talking about here, so perhaps a properly timed voltage differential could be applied to generate the same effect.

Re:Photon Shockwave (1)

pclminion (145572) | more than 8 years ago | (#14491563)

The shockwave propagates through a medium at the same velocity as more conventional compression waves (sound)

No.. By definition shock waves travel faster than the speed of sound in the medium. Eventually enough of the energy of the shock dissipates as heat and the wave drops to sonic speeds, at which point it is no longer considered a shock wave.

Could some kind of supersonic resonance be set up in a piezoelectric crystal? Maybe, although I can't see how it would be done, but in any case I would not describe it as being sonic.

Re:Photon Shockwave (2, Funny)

NanoGator (522640) | more than 8 years ago | (#14486768)

"Makes me wonder if sonic stimulation at the resonant frequency could be an effective low-power LASER equivalent."

Well, I could route it through one of the EPS taps, but it may cause the intertial dampners to destabilize. Damn I wish we had seatbelts.

Re:Photon Shockwave (0)

Anonymous Coward | more than 8 years ago | (#14496279)

Dielectric not peizoelectric. NaCl forms an isometric crystal that doesn't lead to peizoelectricity. It also leaves alot to be desired as a dielectric.

First new method in 50 years? (1)

MrScience (126570) | more than 8 years ago | (#14483772)

What about those newfangled Semiconductor laser devices [google.com] that were all the rage a few years back? Or are they still considered a plain old lasers?

deconstructing the acronym... (2, Interesting)

Quadraginta (902985) | more than 8 years ago | (#14483944)

They are. Moreover, I think the press-release aspect of this report is a little overexcited. We already know you can produce coherent light by any number of stimulating mechanisms, from flashlamps to microwaves to electricity. What's new here seems only to be that a physical shock can also be the "stimulation" in the acronym ("LASER = "Light Amplification by Stimulated Emission of Radiation"). Now, given that we already knew that a physical shock can stimulate incoherent light emission -- hence the phenomenon of triboluminescence, otherwise known as the crunching wintergreen LifeSavers makes sparks effect -- it doesn't seem real surprising that physical shock can stimulate coherent light emission under the right circumstances.

I can believe the simulations establish the possibility of shock-stimulated coherent light emission, but I am very doubty of the amplitude. There's no way they could do the simulation in as much detail and long enough to account for all the side-channels and decay mechanisms in a real crystal. There's a lot of experimental work ahead before this proves to be a solid discovery. But it's a neat little story, nonetheless.

Correct me if I'm wrong... (3, Interesting)

Wilson_6500 (896824) | more than 8 years ago | (#14487463)

I always thought that the THz band of the spectrum was a difficult place to find _any_ sort of sources, so isn't a tunable, non-lasing THz emittier a very significant discovery in and of itself, to say nothing of another source of coherent light?

THz Waves (1)

Anti_Climax (447121) | more than 8 years ago | (#14488112)

I remember Reading previously that scientists were trying to develop a cheap and reliable means of producing Terahertz electromagnetic waves, as they were very useful for imaging, particularly medical. Apparently they have similar properties to x-rays without that pesky ionizing radiation problem.

Read More Here [physicsweb.org]

Re:THz Waves (1)

Sody (940054) | more than 8 years ago | (#14489824)

THz waves are also part of the infrared spectrum, so they would certainly be less damaging to living things. Unfortunately, they also do not penetrate objects as well as X-rays, etc. and so are more difficult to use for imaging technology.

According to wikkipedia (http://en.wikipedia.org/wiki/List_of_laser_types [wikipedia.org] ) there are not currently many lasers that operate even close to this frequency range, (approximately 10-100 micrometers) so this could be a very useful thing. This is getting closer to the microwave and radio wave portion of the spectrum, so it could have some really neat communications uses, perhaps. (More secure communications using a coherent beam, etc?)

Bad choice of headline. (1)

mink (266117) | more than 8 years ago | (#14492753)

I tried to take it seriously, but the only thing I can think of while reading this is this [theonion.com] article.
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