jovan
August 10, 2003, 3:56pm
1
So I was perusing the archive, and I chanced upon this elderly column: http://www.straightdope.com/classics/a2_114.html
In said article, Cecil roundly dismisses the idea of an “audio laser”.
In this thread and this thread , the issue is further discussed.
All that info, however, is obsolete. The audio laser is, for practical purposes, a reality.
The Audio Spotlight , developed at MIT works a lot like an “audio laser”.
Meanwhile, the Hypersonic Sound System creates much the same effect as the audio spotlight.
And furthermore, there’s a Japanese company (damn I can’t remember which one…) that’s putting out their own technology on the market to do the same thing.
So, in short, not “audio lasers” strictly, but stuff that behaves a lot like it is being put on the market.
A laser is more than just a tightly focused light beam: it is a collection of photons all in phase and of the same polarization. There is no audio counterpart because sound doesn’t have polarization. I don’t know why that wasn’t mentioned in the column.
jovan
August 11, 2003, 6:09am
3
Of course, which is why I said that the stuff above is not “strictly” a laser. I just thought it was cool and worthy of mention.
A laser beam is not necessarily polarized. http://electron9.phys.utk.edu/optics421/modules/m7/laser_systems.htm
In a simple helium neon laser with cylindrical symmetry, the output is said to be randomly polarized. Each individual cavity mode has a linear polarization at any one time. However, the overall laser output is a time varying mix of modes of different polarization. Consequently, the beam appears to be non-polarized when integrated over a fairly short period of time.
Although the beam intensity is fairly constant, if the experiment or application involves polarization dependent optics, such as beam-splitters, then large rapid amplitude fluctuations will be apparent. If this is not acceptable, a polarized helium neon laser must be used. A polarized helium neon laser has an intra cavity Brewster window which introduces sufficient loss in the s-plane of polarization (defined by the window) so that only p-polarized output is produced.