Large third-order optical nonlinedrity and fast response of a squarylium dye

The third-order optical nonlinearities and responses of a squarylium dye, 2,4-di-3-guaiazulenyl-1,3-dihydroxycyclobutenediylium dihydroxide, in tetrahydrofuran (THF) solution and in polystyrene (PS) coating films are measured by the femtosecond degenerate four-wave mixing technique under resonant conditions. The molecular hyperpolarizability gamma of the squarylium dye in the THF solution is determined to be 3.0 x 10(-29) esu at 764 nm, and its electronic component gamma(e). is determined to be 1.1 x 10(-29) esu. The third-order nonlinear susceptibility chi((3)) of one of the present PS coating films containing the squarylium dye is as high as 3.1 x 10(-8) esu at 800nm, and its electronic component chi e((3)) is 1.3 x 10(-8) esu.