| The field of efficient second-harmonic generation (SHG) is recently getting renewed attention due to the emerging field of cascading of second-order nonlinearities. Cascading allows all-optical switching, spatial solitary waves, etc., which can be used for all-optical information routing and processing. These applications require operation at the telecommunication wavelengths in the near infrared, where organic materials, such as poled polymers, are promising candidates due to their superior nonlinear optical coefficients. Polymers are also cheap, can be easily processed, and allow integration with semiconductor technology.; This dissertation includes the linear and nonlinear optical material characterization of the polymeric materials, the fabrication of various polymeric SHG devices and the study of the device performance. In particular, the two nonlinear optical (NLO) side-chain polymers based on the chromophores 4-dimethylamino-4{dollar}spprime{dollar}-nitrostilbene (DANS) and Disperse Red 1 are studied.; Cascading as well as SHG applications require high conversion efficiencies that are preferentially achieved in optical waveguides, where the fundamental and second-harmonic waves travel in the same direction (copropagating geometry). These guided-wave devices allow a tight optical confinement, a long interaction length, and access to the diagonal elements of the nonlinear susceptibility tensor {dollar}sbchisp{lcub}(2){rcub}{dollar} simultaneously. This dissertation investigates the two most promising phase matching techniques, quasi-phase matching (QPM) and modal dispersion phase matching (MDPM). It was found that QPM is technologically challenging for poled polymers and typically introduces an excess propagation loss. MDPM is more compatible with polymer fabrication and was successfully demonstrated over a phase matching distance of up to 7 mm. Multilayer spincoating and inverse poling of polymers have also allowed the optimization of the overlap integral. SHG figures of merit comparable to those of ferroelectric materials were obtained. The propagation loss and the poling efficiency have been identified as current limitations. A large improvement is possible through the use of more suitable materials. |
