Highly Efficient Multiphoton Absorption in a new quadrupolar heterocyclic dye

Organic push-pull compounds, with heteroaromatic rings acting as efficient acceptor (A) and donor (D) moieties, have been synthetized for second- and third-order non-linear optical (NLO) activity. Asymmetric push-pull dyes (A-pi-D) , allowed the preparation of highly efficient NLO-phores for frequency-upconverted lasing applications. The symmetric ones (A-pi-D-pi-A, D-pi-A-pi-D) show good two photon absorption (TPA) properties, largely exploitable for optical limiting applications. The goal of our work is to characterize the nonlinear optical properties and to investigate the relation between the structure and the resulting nonlinear response.