Modulated conjugation as a means for attaining a record high intrinsic   hyperpolarizability
  We report on a series of chromophores that have been synthesized with a modulated conjugation path between donor and acceptor. Hyper-Rayleigh scattering measurements of the best molecule show an enhanced intrinsic hyperpolarizability that breaches the apparent limit of all previously studied molecules. 
Javier P\'erez-Moreno, Yuxia Zhao, Koen Clays, Mark G. Kuzyk