A prototype of this microphone was unveiled at the AES show in 2009. It works on the principle of a soundwave altering a 'smokescreen' which is read by a passing LASER beam. It seems that the idea has not progressed to be a commercial reality. Meanwhile, Optoacoustics do have a product that uses a similar (but more practical) idea. Their Crystal mic sends a light from a LED into the mic, which is then returned to a photosensor. The diaphragm interferes with the reflected light, modulating it wrt the sound. Advantages are no EMI, and very long mic cables can be used.
