Interest in crystalline organic semiconductors has increased recently due to their diverse optical and electronic properties which have numerous device applications. Considerable effort has been focused on utilizing the large optical nonlinearities found in many of these materials.1 One crystalline organic semiconductor: 3,4,9,10 perylenetetracarboxylic dianhydride (PTCDA), has been of particular interest due to its excellent electronic properties, giant dielectric anisotropies2 and potential uses in optoelectronic devices. Recent research with PTCDA has yielded considerable success with waveguide structures.3,4 Special properties of PTCDA such as low optical absorption loss at near-infrared wavelengths, environmental stability, and capability of patterning make waveguide integrated devices and organic - semiconductor hybrid devices very attractive.