Nonlinear contrawave mixing devices in poled-polymer waveguides

Abstract

We investigated efficient surface-emitting second-harmonic-generation devices in poled polymers, using a 4-dimethylamino-4′-nitrostilbene side-chain polymer. The investigation included characterization of the linear and nonlinear optical properties of the polymer, design of efficient surface-emitting second-harmonic-generation devices based on poled polymers, development of an efficient in-plane poling technique, and demonstration of surface-emitting second-harmonic generation in poled polymers. As a result, strong field in-plane parallel poling was successfully performed with poling fields over 300 V/μm, which led to a large nonlinearity of 150 pm/V at 1064 nm (near resonance). A thick cover layer and a highly resistive substrate were found to be essential for efficient in-plane poling without breakdown at relatively small fields and significant charge injection. We achieved quasi-phase matching in the transverse direction by fabricating nonlinear–linear multilayer waveguides. Each layer had approximately a 150-nm thickness. The largest second-harmonic power conversion efficiency to date in the poled-polymer devices is 0.6%/W cm, which is comparable with those of semiconductor multilayer devices.