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.