Quantum Lattice Fluctuations and the Linear and Nonlinear Optical Susceptibility of Degenerate Ground State Conjugated Polymers

ABSTRACTWithin the Singles-CI approximation, the perturbation theory expression for γ (the non-resonant third-order nonlinear optical susceptibility) contains a class of terms which correspond to (i) the creation of an s-type exciton (ii) a transition to a p-type exciton, and (iii) a return to the ground state through an s-type exciton. The contribution of these terms to γ is considered in the limit of an infinite chain of polyacetylene. The infinite chain limit is obtained by considering a ring of polyacetylene and allowing the ring size to go to infinity. The limit is approached using three methods, each of which reveals a different characteristic length of the system. The form of the excitons is found to be independent of ring size for rings which are larger than the size of the exciton.

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Quantum Lattice Fluctuations and Nonlinear Optics of Conducting Polymers

MRS Proceedings ◽

10.1557/proc-173-671 ◽

1989 ◽

Vol 173 ◽

Author(s):

J. Yu ◽

B. Friedman ◽

W. P. Su

Keyword(s):

Optical Properties ◽

Nonlinear Optics ◽

Conducting Polymers ◽

Conjugated Polymers ◽

Nonlinear Optical ◽

Molecular Model ◽

Nonlinear Optical Properties ◽

Quantum Lattice ◽

Quantitative Calculations ◽

Lattice Fluctuations

ABSTRACTQuantum lattice fluctuations of conjugated polymers in the form of virtual soliton-antisoliton pairs have important effects on the nonlinear optical properties. Quantitative calculations of nonlinear susceptibilities based on the solitonic molecular model are presented.

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Third Order Nonlinear Optical Susceptibility of Trans-(CH)x: A Degenerate Ground State Conjugated Polymer

MRS Proceedings ◽

10.1557/proc-109-205 ◽

1987 ◽

Vol 109 ◽

Cited By ~ 2

Author(s):

M. Sinclair ◽

D. Moses ◽

K. Akagi ◽

A. J. Heeger

Keyword(s):

Oscillator Strength ◽

Nonlinear Optical ◽

Nonlinear Effects ◽

Fast Response ◽

Charge Carriers ◽

Third Order ◽

Nonlinear Optical Susceptibility ◽

Optical Susceptibility ◽

Degenerate Ground State ◽

Time Regime

ABSTRACTThe promise of conducting polymers as fast response nonlinear optical materials has been recently emphasized [1,3]. Polymers such as polyacetylene, polythiophene and the soluble (and processible) poly(3-alkylthienylenes) contain a high density of x-electrons, and they are known to exhibit photoinduced absorption and photoinduced bleaching, indicating major shifts of oscillator strength upon photoexcitation [2,4]. For polyacetylene, these nonlinear effects have been studied in detail in the picosecond [5a,b] and sub-picosecond [5c] time regime and correlated with the photoproduction of charge carriers through fast photoconductivity measurements [6]. The data have demonstrated ultra-fast response with nonlinear shifts in oscillator strength occurring at times of the order of 10-13 seconds. These resonant nonlinear optical properties are intrinsic; they originate from the nonlinearity of the self-localized photoexcitations [7] which characterize this class of polymers: solitons, polarons and bipolarons [4].

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