Large Third-Order Optical Nonlinearity and Fast Response of aSquarylium Dye

Abstract

The third-order optical nonlinearities and responses of asquarylium dye, 2,4-di-3-guaiazulenyl-1,3-dihydroxycyclobutenediyliumdihydroxide, in tetrahydrofuran (THF) solution and in polystyrene (PS)coating films are measured by the femtosecond degenerate four-wavemixing technique under resonant conditions. The molecularhyperpolarizability γ of the squarylium dye in the THF solution isdetermined to be 3.0×10−29 esu at 764 nm, and itselectronic component γe is determined to be 1.1×10−29 esu. The third-order nonlinear susceptibilityχ(3) of one of the present PS coating films containing thesquarylium dye is as high as 3.1×10−8 esu at 800 nm, andits electronic component χ(3)e is 1.3×10−8 esu.