Thermally stable second-order nonlinear optical polymers

Second-order nonlinear optical copolymers containing p-hydroxyphenyl maleimide (HPMI) or glycidylmethacrylate (GMA) as a comonomer were newly synthesized. Second-order nonlinear optical properties of the poled/cured films were investigated in terms of the second harmonic generation (SHG) and linear electro-optic (EO) coefficient measurement. SHG coefficient, d₃₃ was found ranging from 22 pm/V to 45.5 pm/V at the fundamental wavelength of 1064 nm. EO coefficients, r₃₃ were also measured at 632nm, and 830 nm, wavelength, which were significantly high. To prevent the molecular relaxation of poled polymer, thermal crosslink reaction was induced either using diisocyanate as a crosslinker or by virtue of self-crosslinking reaction between the side chains themselves. Temporal stabilities of second-order NLO coefficients of crosslinked polymer systems were proved much better than those of other side chain polymers.