Comparative study of nonlinear-optical polymers for guided-wave second-harmonic generation at telecommunication wavelengths

We report on the linear and nonlinear-optical properties of 4-dimethylamino -4'-nitrostilbene (DANS), 4-diethylamino-1-nitrobenzyl (DANB), and 4-[N-eth yl-N-(2-hydroxyethyl)]amino-4'-nitroazobenzene) (Disperse Red 1;DR1) side c hain polymers whose second-harmonic generation at the telecommunication wav elength of 1.55 mu m was investigated. Measured ultraviolet-visible-near-in frared spectra were analyzed with an inhomogeneously broadened line-shape m odel, in particular, in the long-wavelength tail of the electronic transiti ons, which determines the absorption loss at the second-harmonic wavelength , The nonlinear-optical coefficients were measured at different poling temp eratures and poling fields by the Maker fringe technique. On the basis of t he measured material parameters we calculated the normalized conversion eff iciencies for guided-wave second-harmonic generation at 1.55 mu m. The DR1 polymer exhibited the best nonlinearity-absorption trade-off, with a calcul ated normalized conversion efficiency of several hundred percent per watt, whereas the figures of merit for DANS and DANB are lower and comparable wit h each other. (C) 2000 Optical Society of America [S0740-3224(00)01809-9].