Poling and characterization of polymer waveguides for modal dispersion phase-matched second-harmonic generation

New multilayer polymer waveguides have been introduced with inverted nonlinear layers for efficient modal dispersion phase-matched second-harmonic generation at the telecommunication wavelength near 1.55 mu m. The nonlinear optical core of the waveguides consists of two modified Disperse Red 1-based side-chain polymers with different glass-transition temperatures. The signs of the nonlinear optical coefficients are different in the two polymers after suitable poling above and between the respective glass transitions, thereby optimizing the overlap integral. The optical nonlinearity profile is controlled by in situ electro-optical measurements during the two poling steps. The successful preparation of inverted layers is verified by electro-optical, pyro-electrical, and second-harmonic-generation thermal analysis. Waveguide losses are low at 1.55 mu m (4 dB/cm) and high at 800 nm (100 dB/cm) because of the residual absorption of the Disperse Red 1-like chromophores. Phase-matched second-harmonic generation has been demonstrated with a large figure of merit, 14%/W cm(-2). Extensive room for improvement in second-harmonic generation is possible with optimized chromophores, because the total conversion efficiency is strongly limited by the harmonic losses in the modified Disperse Red 1. (C) 1998 Optical Society of America.