Donor/acceptor pairs, nonlinear optical

Many organic molecules have been shown to exhibit large nonlinear optical coefficients [15]. Especially interesting for second-order nonlinear optics are molecules with conjugated double bonds and with an electron donor and acceptor attached to opposite ends. The donor-acceptor pair leads to an asymmetry in the molecule that is required for second-order nonlinear effects and introduces a permanent dipole moment ju,. However, arranging these molecules in material systems with large macroscopic nonlinearities is not trivial. As opposed to the case of third-order... 

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