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

Abstract

We report on the linear and nonlinear-optical properties of 4-dimethylamino-4′-nitrostilbene (DANS), 4-diethylamino-1-nitrobenzyl (DANB), and 4-[N-ethyl-N-(2-hydroxyethyl)]amino-4′-nitroazobenzene) (Disperse Red 1;DR1) side chain polymers whose second-harmonic generation at the telecommunication wavelength of 1.55 μm 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 μm. The DR1 polymer exhibited the best nonlinearity–absorption 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.