Guanidine donors in nonlinear optical chromophores

Abstract

The variable refractive index of electro-optic (EO) materials has led to a great deal of research interest. Application of an electric field to EO materials leads to a linear variance in refractive index known as Pockel's effect. When incorporated into devices, these materials serve as an effective vehicle for rapid modulation of optical signals using electrical inputs. Nonlinear optical (NLO) chromophores are the most successful family of organic EO materials. These chromophores are typically comprised of a delocalized pi-electron system that connects electron rich moieties (donors) to electron deficient functionalities (acceptors). Hyperpolarizability (beta) is the component of molecular NLO behavior that is responsible for EO effects. Optimization of NLO chromophores for use in EO materials has proven to be a challenging task because enhancement of beta typically results in reduced stability, decreased transparency to telecommunication wavelengths and other unwanted consequences.A family of NLO chromophores has been synthesized containing novel donor systems based on functionalized guanidines. Some chromophores utilizing these donor systems display larger hyperpolarizabilities than those incorporating conventional donors, yet possess superior transparency and stability properties. The unusual and highly desirable characteristics of these chromophores make them very promising candidates for EO applications.