We report on the linear and nonlinear-optical properties of 4-dimethylamino-4Ј-nitrostilbene (DANS), 4-diethylamino-1-nitrobenzyl (DANB), and 4-͓N-ethyl-N-(2-hydroxyethyl)͔amino-4Ј-nitroazobenzene) (Disperse Red 1;DR1) side chain polymers whose second-harmonic generation at the telecommunication wavelength of 1.55 m was investigated. Measured ultraviolet-visible-near-infrared spectra were analyzed with an inhomogeneously broadened line-shape model, in particular, in the long-wavelength tail of the electronic transitions, which determines the absorption loss at the second-harmonic wavelength. The nonlinear-optical coefficients were measured at different poling temperatures and poling fields by the Maker fringe technique. On the basis of the measured material parameters we calculated the normalized conversion efficiencies for guided-wave second-harmonic generation at 1.55 m. The DR1 polymer exhibited the best nonlinearityabsorption trade-off, with a calculated normalized conversion efficiency of several hundred percent per watt, whereas the figures of merit for DANS and DANB are lower and comparable with each other.

Ridged channel waveguides in KNbO 3 were produced using He ϩ ion implantation, photolithographic masking, and subsequent Ar ϩ ion sputtering. We investigated the linear and nonlinear optical characteristics of the waveguides. The effective mode indices are derived from the refractive index profiles using the effective index method. The losses are investigated as a function of wavelength and of the geometrical parameters channel width and ridge height. A minimum loss of 2 dB cm Ϫ1 is measured at a wavelength of 0.633 m. We investigated the power handling capabilities at visible and near-infrared wavelengths. Second-harmonic generation in these waveguides is studied both theoretically and experimentally with regard to its dependence on the guide fabrication parameters. Phase-matching configurations for blue light second-harmonic generation are evaluated on the basis of the dispersion of the effective mode indices. Overlap integrals are calculated on the basis of the field distributions derived from the refractive index profiles. The minimum effective guide cross section is 25 m 2. A continuous-wave second-harmonic output power of 14 mW at 438 nm was obtained with an in-coupled fundamental power of 340 mW in a 0.73 cm long waveguide, yielding a normalized internal conversion efficiency of 25% W Ϫ1 cm Ϫ2 (13% W Ϫ1). This corresponds to an improvement by a factor of 3 compared to the best results reported for KNbO 3 waveguides up to now.

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The near-infrared absorption of two chromophore functionalized polymers and combinations of seventeen different guest chromophores in seven different organic polymer matrices were investigated to assess the effect of chromophore structure and environment on absorption. The near-infrared absorption losses were found to be dramatically larger by as much as 2-3 orders of magnitude in polymer matrices than in solution. Furthermore, the absorption of the long-wavelength tail appears to be related to the glass transition temperature of the polymer matrix that contains the chromophore. These results are interpreted in terms of inhomogeneous broadening.

We report on the depth profile of the nonlinear optical susceptibility in ion-implanted potassium niobate (KNbO3) waveguides using reflected second harmonic generation from wedged samples. After irradiation the waveguide layer exhibits partial loss of its optical nonlinearity that can be recovered to better than 90% of its value of the virgin crystal by subsequent annealing and repoling. We propose microscopic depolarization due to ion implantation to be responsible for the observed decrease of the nonlinear optical susceptibility.