Polymers and Molecular Assemblies for Second-Order Nonlinear Optics

摘要: In the past decade considerable effort has gone into design, synthesis, and characterization of new materials for second-order nonlinear optics [1,2]. The driving force much this been recognition that extremely large hyperpolarizabilities were associated with certain aromatic π electronic systems [3–5] which could lead to significant applications materials. origin hyperpolarizability, s, attributed charge transfer resonances involving appropriately substituted π-electronic systems. Early theoretical efforts account these properties assumed molecule was a two-level system nonpolar ground state highly polarized first excited [4]. action optical field on described by time-dependent perturbation theory [6]. This approach requires calculating matrix elements dipole moment operator leads straightforward prediction s is proportional oscillator strength transition between states, difference moment. Electronic dispersion also accounted for. While relatively simple provided qualitative agreement many experimental observations [4,7], it apparent refinements needed more accurately properties. Thus use SCF approaches calculate accurate wavefunctions, generation representative states extensive configuration interaction, inclusion pairs greater understanding level confidence in predictive capabilities [8–10].