摘要 : Organic polymeric thin films for photonic applications has been a rapidly exciting area of research over the last decade. Second-order nonlinear optical polymer film is created by aligning the appropriate chromophores into a polym... 展开 Organic polymeric thin films for photonic applications has been a rapidly exciting area of research over the last decade. Second-order nonlinear optical polymer film is created by aligning the appropriate chromophores into a polymeric host medium by poling in an electric field followed by permanent fixation. The poling is usually conducted near T_g but the maintenance of poled order is often difficult even at room temperature because of the relaxation of the chromophore units which destroys the orientation of poled dipoles. It is expected that the rotational relaxation may be affected by polymer structure (cross-linking) and hence T_g, device temperature and possibly gravity which acts like a pressure force capable of modifying rotational transition probabilities. We report here the results of our microgravity experiments which were carried out at the ZARM drop tower facility at Bremen, Germany. Two systems were tested: guest―host system using thermal processing and cross―linked system using photocross-linking processing. Five drops of 4.75 s of microgravity were made and for each drop 15 guest―host samples and nine photo cross-linking samples were processed. The sample thickness was fixed at 2 μm; however, poling field, UV intensity, chromophore type and concentration, poling temperature and cooling rate were varied. The relaxation behavior was monitored using second harmonic generation as a function of time for both the samples prepared at 1 and 10~(-6) g. Improvement of relaxation time was observed for certain samples. Simulations using a modified Robertson―Shimha―Curro theory were also carried out. Qualitatively, experimental results support the simulation hypothesis. 收起