Thick Optical-Quality Films of Substituted Poly acetylenes with Large, Ultrafast Third-Order Nonlinearities and Application to Image Correlation

摘要

Processable organic materials with large, ultrafast third-order susceptibilities, x~((3)). could enable all-optical signal processing (AOSP) applications through either fabrication of large-area thick films or integration into hybrid organic/ silicon photonic devices. Conjugated polymers, such as polyacetylene, have been shown to exhibit large optical nonlinearities upon application of intense electromagnetic fields. Despite these nonlinearities, many conjugated polymers are inadequate for photonic applications because they lack sufficient processability, or form films with significant crystallinity or inhomogeneous morphologies resulting in poor optical quality. For example, although films of unsub-stituted polyacetylene have been found to possess large third-order susceptibilities, they also exhibit extensive cry-stallinity, resulting in poor optical quality and large scattering losses. A more processable soluble diester polyacetylene derivative has been reported; however, only thin films have been produced from this material and the bulky side groups can be anticipated to lead to a reduced nonlinear response through a dilution effect. The diester polyacetylene was successfully used in an image-correlation application performed using degenerate four-wave mixing (DFWM) in the visible region with resonant excitation, although the diffraction efficiency was relatively low, due mainly to the limited interaction length.