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Liquid Crystals and Lasers
Wan2Be writes "A new kind of glass pane that quickly switches from transparent to diffracting and back again. The change is triggered by applying an electric field, so the pane could easily be controlled by the electric signals of a computer, offering a powerful new way to steer beams of light."
Ah, but that's just turning opaque. This stuff doesn't turn opaque, it refracts. This allows for not just blocking the light but reaiming/controlling it as well.
... without any order in the drop size and spacing, these older liquid crystal systems simply scatter light in all directions ... In our case, ... we're able to steer light in specific directions"
Very similar concept, almost identical process, but quite a difference overall.
If you bother to RTFA, it says:
"The big difference between what we do and what has been done before is that older-style glass panes contain a random distribution of drops and drop sizes
=Smidge=
Liquid crystals are really slow. You really have to struggle to get 35 ms switching out of them, which is what the movie people want. These diffraction switches are a lot faster, but I doubt they'll ever get faster than 0.5 ms.
The basic problem is that you're dealing with long strands of polymers which orient themselves almost but predictably not quite parallel to each neighboring polymer strand, unless a current is flowing, in which case they just align strictly parallel to each other. It takes time, lots of time, for the reconfiguration to occur, because it is a fundamentally mechanical process.
The article cited did a horrible job IMHO of representing the underlyng science. The regularity of the crystal droplets has nothing to do with the new effect -- which is using a thinner layer of liquid crystals to difract instead of polarize, which requires thicker LCs. The droplet regularity is an artifact of the thinness, not a cause of the essential property as is purported.