US Patent 7889413 - Field generating nanoparticles doped in light valves

http://www.freepatentsonline.com/7889413.html

This patent from the U.S. Air Force teaches using nanoparticles to construct a new type of optical switch. Claim 1 reads:

1. A method for automatically activating an optical light valve, the method comprising:

providing a photorefractive cell having a birefringent medium which is doped with nanoparticles;

transmitting light through the photorefractive cell to create an electric field in the photorefractive cell such that the alignment state of the birefringent medium and nanoparticles is changed to thereby reduce the intensity of the light being transmitted therethrough,

wherein the intensity of light is reduced by dispersing the light without an external power source.