Abstract

Delocalization of the excitation in molecular aggregates is explained as a Frenkel exciton picture. Especially, J aggregates of pseudoisocyanine bromide (PIC-Br) have the narrowest absorption band at low temperature.¹ Nonlinear optical (NLO) responses of PIC J aggregates under the resonant excitation show the dispersive spectra, the absorption saturation observed at the long wavelength side of the J band and the induced absorption observed at the long wavelength side of the J band.^2,3 The optical nonlinearity observed at a fixed wavelength, J band show the inverted region, in which the NLO properties decrease with the increase of the excitation intensity.⁴

© 1995 IEEE