Dynamic optical gratings using photomechanical molecular crystals

Spatially controlled photomechanical deformations on the surface of a single photomechanical crystals can be used to actively control light propagation. Single crystals composed of the organic molecules 1,2-bis(2,4-dimethyl-5-phenyl-3-thienyl)-3,3,4,4,5,5-hexafluoro-1-cyclopentene and 4-fluoro-9-anthracenecarboxylic acid are used as reversible beam control elements. This is accomplished by using either electron beam lithography to imprint a fixed pattern with a switchable period, or a digital micromirror array to reversibly imprint an arbitrary pattern ion the crystal surface, which then erases itself due to thermal back-reaction. Both of these approaches allow one light source to control the direction and intensity of a diffracted 633 nm probe laser.