Synthesis and characterization of a novel nonlinear optical polyurethane polymer

A cross-linked polyurethane with a novel nonlinear optical (NLO) chromophore [2-(4′-N,N-dihydroxyethylphenylazo)-3,5-dinitrothiophene] covalently incorporated for second-order optical nonlinearity was developed. High optical-quality films can be obtained from the prepared polymer. Resonance-enhanced second-harmonic coefficient (d33) of 66 pm V−1 at 1.064 μm fundamental wavelength of the poled films was obtained. Test on temporal stability shows that when the films were kept in an oven at 100°C for 1000 h in air, 75% of the NLO signal still remained.