title: Nonlinear Optical Properties of X(C6H5)4 (X = B(-), C, N(+), P(+)): A New Class of Molecules with a Negative Third-Order Polarizability.
abstract: Organic π-conjugated materials have been widely used for a variety of nonlinear optical (NLO) applications. Molecules with negative real components Re(γ) of the third-order polarizability, which leads to nonlinear refraction in macroscopic systems, have important benefits for several NLO applications. However, few organic systems studied to date have negative Re(γ) in the long wavelength limit, and all inorganic materials show positive nonlinear refraction in this limit. Here, we introduce a new class of molecules of the form X(C6H5)4, where X = B(-), C, N(+), and P(+), that have negative Re(γ). The molecular mechanism for the NLO properties in these systems is very different from those in typical linear conjugated systems: These systems have a band of excited states involving single-electron excitations within the π-system, several of which have significant coupling to the ground state. Thus, Re(γ) cannot be understood in terms of a simplified essential-state model and must be analyzed in the context of the full sum-over-states expression. Although Re(γ) is significantly smaller than that of other commonly studied NLO chromophores, the introduction of a new molecular architecture offering the potential for a negative Re(γ) introduces new avenues of molecular design for NLO applications.
authors.affiliation: †School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, United States.
authors.forename: Rebecca L
authors.initials: RL
authors.lastname: Gieseking
authors.affiliation: ‡CREOL, The College of Optics and Photonics, University of Central Florida, Orlando, Florida 32816, United States.
authors.forename: Trenton R
authors.initials: TR
authors.lastname: Ensley
authors.affiliation: ‡CREOL, The College of Optics and Photonics, University of Central Florida, Orlando, Florida 32816, United States.
authors.forename: Honghua
authors.initials: H
authors.lastname: Hu
authors.affiliation: ‡CREOL, The College of Optics and Photonics, University of Central Florida, Orlando, Florida 32816, United States.
authors.forename: David J
authors.initials: DJ
authors.lastname: Hagan
authors.affiliation: †School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, United States.|§Department of Chemistry and Center for Applied Energy Research, University of Kentucky, Lexington, Kentucky 40506-0055, United States.
authors.forename: Chad
authors.initials: C
authors.lastname: Risko
authors.affiliation: ‡CREOL, The College of Optics and Photonics, University of Central Florida, Orlando, Florida 32816, United States.
authors.forename: Eric W
authors.initials: EW
authors.lastname: Van Stryland
authors.affiliation: †School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, United States.
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Brédas