Polyphenylene ether based thin-film nonlinear optical materials having high chromophore densities and alignment stability

Current generation polystyrene-, polyacrylate-, and polyethylene-based⁵ materials are intrinsically limited in a designed functionalization level to a maximum of one chromophore molecule per repeat unit (in most cases, considerably less has been achieved) and to architectures having undesired residual chain mobility, as suggested by T_g data. This paper addresses several of these issues and describes the synthesis and characterization of a new class of highly functionalized SHG polymers derived from the robust, high-T_g (205-210°C) thermoplastic poly(2,6-dimethyl-1,4-phenylene oxide) (PPO). To better define the transparency characteristics of the subject films, the authors also report the fabrication of a waveguide. Preliminary waveguiding experiments were performed on several PPO-NPP films to better define their optical characteristics. A planar waveguide structure consisting of air/film/glass layers was used. The waveguide modes were excited with a He-Ne laser (0.633 μm) using prism-coupling techniques with SF6 glass (n = 1.797) prisms as the couplers. The refractive index of the films was determined from the coupling angles of various waveguide modes.