Metalloporphyrins for quadratic nonlinear optics

Abstract

Cu^II- and Zn^II-based donor-acceptor porphyrins have been examined for second-order nonlinear optics using the hyper-Rayleigh scattering technique at 1064 nm. Introduction of the metal ions enhances the first hyperpolarizability (β) of the free-base donor-acceptor porphyrins significantly. The open shell Cu^II (d⁹) has a greater influence on β of these porphyrin systems than the closed shell Zn^II (d¹⁰). The high β values in the Zn^II porphyrins are understood in terms of the change in dipole moments upon excitation within the context of the two-state model as well as two-photon resonance enhancement. In Cu^II porphyrin complexes a large number of excited states seem to contribute to β with, perhaps, a little contribution from two-photon resonance at the excitation wavelength.