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Proceedings Paper

Role of electron-electron interactions in the nonresonant nonlinear optical response of conjugated polymers
Author(s): Eric E. Moore; David Yaron
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Paper Abstract

The origin of the large third-order nonresonant nonlinear optical response of conjugated polymers is explored using single configuration-interaction (S-Cl) theory to solve the Pariser-Parr-Pople (PPP) Hamiltonian of polyacetylene. Both the strength of electron-electron interactions and the degree of bond alternation are treated as free parameters. For a fixed bond alternation, increasing the strength of electron-electron interactions from zero to 150% of that typically used in PPP theory decreases the hyperpolarizability by nearly two orders of magnitude. However, this decrease arises primarily from an increase in the optical gap. When the bond alternation is adjusted such that the optical gap remains fixed, increasing the strength of electron-electron interactions changes the hyperpolarizability by less than 30%. For a wide range of parameters, there is good agreement between Hückel theory and PPP theory, provided the Hückel gap is parameterized to the PPP optical gap. In PPP theory, the hyperpolarizability is nearly proportional to the optical gap raised to the -5.5 power, as compared to the -6 power for Hückel theory. These results suggest that electron-electron interactions need not be explicitly included in a model of the nonresonant response of polymers, but can instead be absorbed into the effective parameters of an independent electron model.

Paper Details

Date Published: 13 October 1997
PDF: 10 pages
Proc. SPIE 3147, Nonlinear Optical Properties of Organic Materials X, (13 October 1997); doi: 10.1117/12.279312
Show Author Affiliations
Eric E. Moore, Carnegie Mellon Univ. (United States)
David Yaron, Carnegie Mellon Univ. (United States)


Published in SPIE Proceedings Vol. 3147:
Nonlinear Optical Properties of Organic Materials X
Mark G. Kuzyk, Editor(s)

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