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There are several ways to directly convert acoustic/mechanic signals into optic signals (e.g. opening/closing a shutter, or the acousto-optic effect). Is there any way to do the reverse, without using photoelectric effects or other electric effects/electricity as intermediate?

I suppose one way would be to use the thermal heating from the light to deform e.g. a bimetal, but I doubt that will work with the light intensity of fiber-optic signals and it would probably be limited to low frequencies. Or am I wrong with that?

edit: background: This is purely theoretical. I'm exploring what the world would look like if we did not use electricity. While the acousto-optic effect can modulate sound onto a laser beam, I haven't found a way to do the reverse except by using electrical components.

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  • $\begingroup$ Would a crystal radio satisfy your restrictions? Perhaps not since electricity is involved. How about a piezo sensor launching a surface wave? Or is the piezo effect considered electricity? Of course, a high enough power laser creates audible effects when it hits somethng. What are your real constraints? What are you really trying to do? $\endgroup$ – Jon Custer Aug 3 '17 at 13:26
  • $\begingroup$ I don't really understand your examples. How is opening/closing a shutter going from mechanical to optic signals? Closing a shutter based on light would likely require some electronics to start the circuit and some sort of actuating device. Your acoustio-optic effect seems to also use electricity. $\endgroup$ – JMac Aug 3 '17 at 13:40
  • $\begingroup$ Use film as an amplifier: expose a moving strip of film to record the modulation, develop it, now run that film under a powerful light (such as the sun) which can for instance heat a bimetallic strip. You may want several stages of amplification, but this is easy enough to do. $\endgroup$ – tfb Aug 3 '17 at 13:59
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    $\begingroup$ @JMac By opening/closing a shutter you can send on/off keyed messages by light, e.g. morse code. My question is about going the other way, e.g. if sound is encoded in the intensity of a laser, how to get the sound back. The acousto-optic effect is that the refractive index of some materials change if pressure is applied to them. The link is to an acousto-optic modulator that first uses a piezo to transform an electric input to pressure. $\endgroup$ – JanKanis Aug 3 '17 at 16:48
  • $\begingroup$ @JMac Google for "Aldis Lamp". $\endgroup$ – Solomon Slow Aug 3 '17 at 17:00

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