Lasers: Leaving Light Behind

This entry was posted by Thursday, 25 February, 2010
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One NOISY Laser

Optics: The Phonon Laser


I guess you’re not impressed by lasers.

You’ve got an $8.95 laser pointer from Job Lot. You had some hair removed by a laser. There’s one in your CD player. And they’re inside of things that’re all over your house. You even use one to drive the cat WACKY. And I wish you wouldn’t.


I’ll take a minute here to explain the difference between a laser and, say, an electric light.

Until 1958, when the laser was invented at Bell Labs, all forms of artificial light were “incoherent”. Incoherent light consists of light waves that don’t “line up” particularly well. The crests and the valleys of the waves are “all over the place” as opposed to coherent light where all the crests and valleys DO line up with each other.

What’s the difference? When light is coherent, it behaves itself. Instead of spreading (converging), it remains packed into a tight beam.

Not much of  a difference, I admit. But it makes the light kinda “pure” and “monochromatic” (one and only one frequency)  as opposed to a flashlight which is a great big MESS of frequencies. And a laser light doesn’t spread out the way we’re used to a light beam behaving; instead it just stays in a tight beam.  The science behind it is NICELY described in an article in HOW STUFF WORKS. Which I appreciate because MISTER ScienceAintSoBad is in NO mood to go through all the details, this morning.

The fact that monochromatic laser light DOESN’T  dissipate its energy by spreading out like its more ordinary cousins means it can transmit great power over a long distance or offer real  accuracy for measuring stuff. Its nice tight beam is even useful for communications since it can illuminate light fibers or bounce off of distant targets and still hold onto its properties.

Who would a thought that a laser, which is, after all, just a humble beam of light, would turn out to be so important?


The length of a light wave is short.  It’s measured in billionths of a meter. Wanna see how the wavelength varies with color? (Probably not, but just in case, this is fun. )

Frequency, for frequency, the wavelengths of sound are even shorter.  Much, much shorter.  So sound  could be used for WAY more accurate measurements in medicine and other applications.  And a sound-based laser (phonon laser) would, no doubt, have other startling tricks it could do besides measurement, if we really had one.


Phonon lasers still aren’t available at Job Lot but the work’s movin’ along VERY nicely.  It’s described in Physical Review Letters (who NAMES these publications?)  and in Physics.

Mister ScienceAintSoBad thinks the emergence of the phonon laser is now likely.  Whole new industries will follow.

ScienceAintSoBad Rating= 10

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