Photorefractive Effect

Published on: Wed Jun 08 2011

The photorefractive effect is incredible. When light from a split beam is shone in through the orthonormal sides of a photorefractive material the interference pattern creates dark and light zones throughout the crystal.  The electrons become excited in the bright areas and concentrate in the dark zones. This pattern becomes fixed in place and the refractive index changes depending on the concentration of the electrons throughout the crystal. This forms a 3D diffraction grating. Shining a two new lights through the crystal recreates the original pattern of light.

There are several things I had not known here. I did not know that shining two beams from a single source through a crystal would form an interference pattern. Of course I can understand why this would happen, I'm just not sure why I never thought to try it out.

The electrons gathering in certain areas changes the refractive index. I hadn't thought about how the refractive index of a material works on the atomic level.

An internal space charge field develops! This means the electrons are trapped in the new formation!

It is a type of memory. And I could erase it and do it over and over again to the crystal. I need a special type of crystal. LiNbO3. Lithium Niobate.

Tomorrow I'm going to try observing interference in a material.

Just in case I need this link later, 3D light sculpting system out of MIT (Like a 3D graphics tablet) w/ force feedback)

Does it matter what sides(s) I shine the new lights through to recreate the effect? If I shine a blue, red and green lasers through different sides will I create color? Could I put polarizing filters over the front? What if I put the polarizing filters used in LCD screens? Could I change the saturation levels then?