New non-dipolar structures with significant quadratic hyperpolarizabilities

'Octupolar' molecules are of particular interest in the field of nonlinear optics due to their potentially large quadratic nonlinearities. Within this framework, we have designed organic chromophores of tetrahedral symmetry and investigated their quadratic nonlinearities by performing harmonic light scattering (HLS) experiments in solutions. Issues related to the molecular engineering of the nonlinearity-transparency trade-off have been addressed. As a result, molecules combining significant quadratic hyperpolarizabilities and excellent transparency have been identified. (C) 1998 Elsevier Science B.V.