Large Non Resonant Nonlinearities in DANS Based Polymer Waveguide: Role of Microscopic Cascading,
UNIVERSITY OF CENTRAL FLORIDA ORLANDO CENTER FOR RESEARCH IN ELECTRO-OPTICS A ND LASERS
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Polymers can exhibit both large and fast nonresonant third-order nonlinearities which rely on Pi-electron delocalization and conjugation, as well as good physical and chemical properties suitable for the fabrication of nonlinear integrated optics devices. Soluble polymers with strong charge transfer states such asymmetrically substituted 4-dialkylamino-4-nitro-stilbene DANS and 4-dialkylamino-4-nitro-diphenylbu-tadiene DAN2 side-groups were originally developed for electro-optic applications because of their large second order nonlinearities and low propagation losses in waveguide form. Using nonlinear grating coupling we found a large value for n sub 2, the Kerr coefficient. Measurements and analysis of the spectral dispersion of third harmonic generation indicate that the dominant contribution to the nonlinearity is due to the local cascading of second order nonlinearities.