NOVEL THERMALLY STABLE CROSS-LINKED NONLINEAR-OPTICAL SILICA FILMS PREPARED BY A SOL-GEL PROCESS

To improve the orientational stability of the chromophore induced by a n electric field in a second-order nonlinear optical polymer, we have synthesized a thermally stable and crosslinkable azo dye, 4-[(4 onyl]- 4'-[N,N-bis(2-hydroxyethyl)amino]azobenzene. The transparent films wit h silica as matrix and organic chromophore as cross-linking agent were then prepared by using a sol-gel process. The resulting films heated at 200 degrees C under a high-corona field exhibited the nonlinear opt ical coefficient d(33) = 32 pm/V in Maker-fringe measurement. Long-ter m stability of second-harmonic coefficients in these films was observe d even at 160 degrees C.