Ultrafast nonlinearoptical response of squarylium dye J-aggregates and fabrication of their LB-films

Controls of mesoscopic structure of organic dye molecules such as formation of the J-aggregates are important for the purpose of achieving highly efficient and ultrafast nonlinear-optical properties. Squarylium dyes with alkyl substituents form J-aggregates with highly ordered two-dimensional structure in their monomolecular layer on water surface (Langmuir film). By absorption saturation measurement using femtosecond pump-probe method, 30 times larger and 10 times faster optical responses than their solution in chloroform were observed for the J-aggregates. We also succeed in transferring the Langmuir film on a glass substrate for a LB-film using post surface coating by poly-purfluorocarbon. This LB-film, which preserves two-dimensional structure, also exhibited similar femtosecond responses to the Langmuir film.