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1 December 1991 Dispersion of x(3) in fused aromatic ladder polymers and their precursors probed by third-harmonic generation
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Third harmonic generation (THG) experiments have been performed on a variety of conjugated organic materials over the energy range 0.5 - 1.5 eV. The measured dispersion of (chi) (3)(-3(omega) ;(omega) ,(omega) ,(omega) ) is presented and comparisons between structurally related materials are made to elucidate structure-property relationships. In the benzimidazobenzophenanthroline material series consisting of the fully fused ladder polymer BBL, the semiladder polymer BBB, and the model molecule cis-BB, the effects of polymerization and ring fusion are observed. The cis-BB displays an interference in the THG spectrum, while this feature is absent in the BBB and BBL. The difference in the nonlinearity of the BBB and BBL is attributed to the difference in the number density of the two materials. The effect of the ladder structure on the nonlinearity is demonstrated by comparing the nonlinearity of BBL with PPI, a polyazomethine possessing a similar backbone. The ladder structure increases the nonlinearity by a minimum factor of 5 throughout the energy range examined. The effect of donors on the polyazomethine backbone is examined using the hydroxy and methoxy donors. The methoxy donor increases the nonlinearity, while the hydroxy donor reduces the nonlinearity. The physical implications of these observations are discussed.
© (1991) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Jeffrey S. Meth, Herman A. Vanherzeele, Samson A. Jenekhe, Michael F. Roberts, Anil K. Agrawal, and Chen-Jen Yang "Dispersion of x(3) in fused aromatic ladder polymers and their precursors probed by third-harmonic generation", Proc. SPIE 1560, Nonlinear Optical Properties of Organic Materials IV, (1 December 1991);


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