ULTRAFAST EXCITON DYNAMICS IN HIGHLY ORIENTED POLYDIACETYLENE FILMS

The nonlinear optical response in uniaxially oriented films of poly[1. 6-di(N-carbazolyl)-2, 4-hexadiyne], epitaxially grown on a potassium a cid phthalate single crystal, has been measured by femtosecond pump an d probe. A fast initial relaxation and the formation of long-lived spe cies at high excitation intensities have been observed. A high third-o rder nonlinear optical susceptibility of 2 X 10(-7) esu has been estim ated at 627 nm. The effects of sample orientation on the relaxation dy namics have also been investigated.