Soft-optoelectronics Materials: Efficient Utilization of Molecular Alignment by Prism Couplers

Abstract

Very large two-beam coupling gain (Γ) and also a small grating spacing were obtained with a low driving voltage in a photorfractive polymer having low glass transition temperature (T_g) in a novel device structure using prism coupling. A net gain-length product (Γ-α)L (L: interaction length), close to 1 was obtained at an external electric field of <40 V/μm and at a grating spacing of 0.42 μm. A mechanism to bring the enhancement was explained by optimized parameters, effective electro-optic coefficient, phase shift, space-charge field, and effective interaction length, compared with a conventional device structure. Moreover, prism coupling technique was found to be applicable to utilize the molecular alignment in low-T_g polymeric materials, "soft-optoelectronics materials".