Abstract

Early theoretical^1-6 and experimental^1,2,7,8 studies have pointed out the interest of highly extended conjugated molecules (e.g., polyenes) for optimization of nonlinear quadratic (β) and cubic (γ) hyperpolarizabilities at the molecular level. The role of the conjugation length, of the bond alternation, and the influence of side or chain-end substituents was intensively explored using various theoretical methods. However, the experimental investigations that would be required to validate these models remained limited to short-length oligomers, owing to the poor stability of polyenic moieties beyond a limited number N of carboncarbon double bonds, and to solubility problems occuring with long-chain conjugated compounds. Therefore, nonlinear optical studies remained limited to oligomeric species up to N = 16.

© 1994 IEEE