OPTIMAL SYNTHETIC DESIGN OF 2ND-ORDER NONLINEAR-OPTICAL MATERIAL WITHGOOD TEMPORAL STABILITY

Second-order nonlinear optical copolymers containing p-hydroxyphenyl m aleimide or 4-cinnamoyloxy-phenylmaleimide as a comonomer were newly s ynthesized. For improving the temporal stability, we adopted the cross link reaction thermally and photochemically. Second-order nonlinear op tical properties of the poled/cured films were investigated in terms o f the second harmonic generation (SHG) and linear electro-optic (EO) c oefficient measurement. SHG coefficient, d(33) was found to be 14 pm/V at the fundamental wavelength of 1064 nm and EO coefficient, r(33) wa s found to be 25-30 pm/V at 633 nm wavelength in two different crossli nked structures. To prevent the orientational relaxation of poled poly mer, thermal crosslink reaction was induced using diisocyanate as a cr osslinker between the side chains themselves. Another photo-crosslink was induced exposing the film at 257 nm wavelength during poling. Temp oral stabilities of second-order NLO coefficients of crosslinked polym er systems were proved much better than that of guest-host system or o ther side chain polymers.