Abstract
Third-order nonlinear optical (NLO) properties of quinoid dyes were studied by third harmonic generation measurement. A large (chi) (3)(-3(omega) ;(omega) ,(omega) ,(omega) ) value of 4.8 X 10-11 esu was found on 2,6-di(n-butylamino)-4,8-dihydroxy-1,5-naphthoquinone and contribution of the `Molecular Strip' through intermolecular hydrogen bonds to the large NLO property was suggested from crystal structure analysis. According to the suggestion, we evaluated (chi) (3)(-3(omega) ;(omega) ,(omega) ,(omega) ) values 1,4- dithioketo-3,6-diphenyl-pyrrolo-[3,4-c]-pyrrole, which also form the `Molecular Strip', to be 1.7 X 10-11 esu.