Spatial Photocontrol of the Optical Output from an Organic Crystal Waveguide

The versatility in mechanical properties and the capability of optical waveguiding of molecular crystals have attracted research on the potential application of these materials in optomechanical transduction. Here, we demonstrate spatial photocontrol over the optical output from slender single crystals of an azo compound, 3',4'-dimethyl-4-(dimethylamino)azobenzene that can be used as a crystalline optical waveguide. The position of the free end of a single crystal can be controlled through reversible photoswitching between the trans and cis isomers at the irradiated crystal surface. The passive optical waveguiding capability of the crystal remains unaffected by its deformation induced by exposure to UV light. Moreover, the response time of the material by bending upon irradiation can be thermally regulated to control the positioning of the tip of the crystal. These single-crystal organic actuators with dual (optical and photomechanical) response deliver on the long sought for dynamic all-organic optical elements to be incorporated in microcircuits.