CORRELATION BETWEEN POLYMER ARCHITECTURE AND SUB-GLASS-TRANSITION-TEMPERATURE LIGHT-INDUCED MOLECULAR-MOVEMENT IN AZO-POLYIMIDE POLYMERS - INFLUENCE ON LINEAR AND 2ND-ORDER AND 3RD-ORDER NONLINEAR-OPTICAL PROCESSES

We report on light-induced linear and second-and third-order nonlinear optical effects in high-glass-transition-temperature (T-g) photosensi tive nonlinear optical azo polyimides. We present evidence of light-in duced orientation of azo chromophores at room temperature in very high -T-g polyimides (T-g up to 350 degrees C) even though the chromophore is firmly embedded into the polymer backbone. We show that the isomeri zation reaction and the light-induced polar and nonpolar orientation d epend on the molecular structure of the unit building blocks of the po lymer. The mechanism of the photoassisted poling process is clarified, and it is shown how the linear and second-and third-order nonlinear o ptical effects can be controlled by light. (C) 1998 Optical Society of America.