Abstract

The polyene trans-β-carotene has become a standard in the study of third-order nonlinear optical properties of organic compounds.¹ It shows one of the largest instantaneous off-resonant nonlinearities reported to date. The most common approach to enhancing this nonlinear response has been to increase the electron conjugation with longer backbones.² However, it has been recognized recently that removing the center of molecular symmetry represents another feasible route to increasing the third-order susceptibility without deleterious effects, such as smaller molecular densities, an increased molecular instability, and poor solubility.³ This approach changes the relative contributions of the one- and two-photon resonances associated with states of mixed symmetry, enhancing the positive contributions to the nonlinearity. Here we report an enhancement of up to approximately a factor of 50, which is to our knowledge one of the largest enhancements reported to date. Indeed, extrapolations to, for example, a 40%-loaded side-chain polymer could produce a material with one of the largest third-order susceptibilities known.

© 1995 Optical Society of America