Molecular aggregates have the potential applications on nonlinear optics and integrated optics. Unique properties of one dimension nanostructure dye molecular J-aggregates are different from either monomers or bulk materials. The unique optical properties of molecular aggregates

not observed in crystals are superradiant emission and giant optical nonlinearities. Superradiance is caused by the fact that the oscillator strengths of the coupled molecules are swept together in a few eigenstates

which thus obtain agiant transition dipole to the ground state and are therefore superadiant: their radiative decay rate enhanced linearly with the number of coupled molecules N. Absorption of aggregates and superradiance are resonant in the spectra. The nonlinear refractive index

absorption coefficiency and polarizibility were measured with Z-scan.It is observed that three order nonlinear polarizibility was increased with chain lengths shortening and the mechanism was analyzed and discussed.