Study of Third-Order Microscopic Optical Nonlinearities in Sequentially Built and Systematically Derivatized Structures.

摘要

With a goal of understanding the structure-property relationship for third-order microscopic optical nonlinearity, we have investigated the nonlinearities of a number of sequentially built and systematically derivatized n conjugated structures by using degenerate four-wave mixing. To examine the nature of effective conjugation, we have measured the third-order microscopic nonlinearities, gamma, for several para polyphenyls and compared the dependence on the number of repeat units with that observed in the alpha-thiophene oligomers. Our results show that while the limiting conjugation length in each conjugated series may be different, it becomes much shorter for polyphenyls than for polythiophenes. Systematically derivatized alpha-terthiophene structures have also been investigated. The substitution of a pyrrole or a benzene unit in the place of the central thiophene ring in the alpha-terthiophene structure reduces the gamma value. (rrh)