A PHOTOREFRACTIVE POLYMER WITH HIGH OPTICAL GAIN AND DIFFRACTION EFFICIENCY NEAR 100-PERCENT

PHOTOREFRACTIVE materials are of considerable interest for the develop ment of all-optical devices(1). The photorefractive effect appears in materials that exhibit an electric-field-dependent refractive index an d that are photosensitive, such that the spatial distribution of photo generated charge carriers is modified on irradiation with light. The d iffraction pattern formed by the interference of two coherent light be ams within such a material generates a nonuniform internal electric fi eld that in turn modulates the refractive index. The resulting refract ive-index pattern forms a grating that can diffract Light and thereby give rise to two-beam coupling, whereby one of the writing beams gains energy at the expense of the other-a property that can be exploited i n photonic devices. Although the best photorefractive materials curren tly available are inorganic crystals such as LiNbO3, there is consider able interest in the development of photorefractive polymers(2-8), owi ng to their structural flexibility, ease of processing and lower cost. We describe here a polymer composite with excellent photorefractive p roperties. We have achieved a diffraction efficiency approaching 100% and a net two-beam coupling gain of more than 200 cm(-1), making these polymeric materials suitable for immediate application in areas such as dynamic holographic storage and optical information processing(1).