Is there such an optical filter that is sensitive to mechanical force exerted on the material?

Question

Normal optical filter blocks some range of light frequency. Filter characteristics is static and never changes.

What I'm looking for is a filter with variable characteristics which is sensitive to mechanical force exerted on it. For example, if a filter is stretched outward, its filtering range moves as the strech continues.

Am I dreaming? Looking at the eye glasses that is darkened when you are outside and gets light when inside, hopefully I'm not.

Answer 1

Yes , there are plenty of photoelastic substances around. They are mostly used in thin films to produce interference patterns when parts are stressed. Here's a really interesting paper from a few years ago about a novel use of one of these films :

http://polypedal.berkeley.edu/twiki/pub/PolyPEDAL/MechanicsResearch/jeb9681_singleleg.pdf

Answer 2

It doesn't involve a static force, but there are things called Acousto-Optic Tunable Filters (google that) that pass a narrow band of optical wavelengths based on the frequency of sound waves exciting the (crystalline) filter. It 's based on a diffraction pattern set up in the crystal by periodic compression of the lattice affecting it's local index. The acoustic frequency is very high, though, 10's of megahertz.