LARGE 1ST HYPERPOLARIZABILITIES IN PUSH-PULL POLYENES BY TUNING OF THE BOND-LENGTH ALTERNATION AND AROMATICITY

Conjugated organic compounds with 3-phenyl-5-isoxazolone or N,N'-diethylthiobarbituric acid acceptors have large first molecular hyperpolarizabilities (beta) in comparison with compounds with 4-nitrophenyl acceptors. For example, julolidinyl-(CH=CH)3-CH=N,N'-diethylthiobarbituric acid, which has 12 atoms between the donor and acceptor, has a beta(0) of 911 X 10(-30) electrostatic units, whereas (CH3)2NC6H4-(CH=CH)4-C6H4NO2, with 16 atoms between its donor and acceptor, has a beta(0) of 133 x 10(-30) electrostatic units. The design strategies demonstrated here have resulted in chromophores that when incorporated into poled-polymer electrooptic modulators exhibited significant enhancements in electrooptic coefficients relative to polymers containing the commonly used dye Disperse Red-1. Poled polymer devices based on these or related chromophores may ultimately lead to high-speed electrooptic switching elements with low drive-power requirements, suitable for telecommunications applications.