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I'm curious if there is a material that is porous to light, but only when it is slightly deformed / vibrating. Do such materials exist? In particular I want to prevent a (cheap) laser's light from penetrating (source hitting the material on line perpendicular to surface) until some vibration occurs. I am an experimental musician with a weird idea to create some neat sounds, but I am not sure if this is even technically possible.

I am aware of photoelastic materials but I don't think what I am describing exactly fits that category, or at least not as typically described or used, but maybe I am wrong.

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  • $\begingroup$ What about a metal membrane with lots of parallel interleaved slits, so that when pulled orthogonally to them they extend into lozenge-shaped holes, like a net? $\endgroup$ Jan 7, 2022 at 22:15
  • $\begingroup$ This is definitely something I thought about - a simple prototype I could build at home is a thin surface of any adequately opaque material with a single slit, delicately cut. Multiple slits would probably perform significantly better. I would need to be confident that such a membrane's slits would return to their original form... $\endgroup$
    – gdoug
    Jan 7, 2022 at 22:27
  • $\begingroup$ Maybe you could achieve something like what you want by reflecting the laser beam off a tightly stretched metalized plastic film. Sound waves in the air would make the film vibrate, changing the direction and the spread of the beam. The cheap way to get the film is to buy a metalized toy balloon. $\endgroup$ Jan 7, 2022 at 23:00

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You could use polarized filters ... Yes, just like they make sunglasses out of. If you have two pieces of it and counter rotate them, you can block or allow light to pass through. Imagine they are like venetian blinds (they're not, but pretend they are...)

Watch what this guy does at the 6:41 mark of this video: https://www.youtube.com/watch?v=PJHCADY-Bio

Those polarized filters cost a few pennies, can buy on Ebay easily.

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Another option (so I give it a different answer!) is a lenticular lens. These are common in childrens toys. Pairing one of these up with a selectively slotted aperture would do what you want using linear motion (as opposed to the rotation needed in my first polarizer answer)

https://www.youtube.com/watch?v=DXRqQySFI5Y

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