3RD-ORDER AND 5TH-ORDER OPTICAL NONLINEARITIES IN ORGANIC MATERIALS

We measure the nonlinear optical properties of solutions of a bisbenze thiozole-substituted thiophene compound (BBTDOT) and didecyloxy substi tuted polyphenyl (DDOS) using the Z-scan technique with 532 nm picosec ond pulses. Both compounds exhibit two-photon absorption (2PA) and exc ited-state absorption (ESA) from the 2PA generated excited states. We measure the magnitude and sign of the real (refractive) and imaginary (2PA) parts of the third-order hyperpolarizability, and the excited-st ate absorptive and refractive cross sections. We observe third-order s elf-focusing in BBTDOT and self-defocusing in DDOS while both show exc ited-state defocusing. All these effects were previously observed and modeled in semiconductors giving insight into the nonlinearities occur ring in these organic materials.