Quadratic electro-optic non-linearity of a conjugated porphyrin polymer measured in the Q-band one-photon resonance region



We reprot linear and non-liner optical experiments on a new edge-linked porphyrin polymer that is soluble in pyridine/chlorinated solvent mixtures and that produces optical quality thin films by spin coating. This linear absorption properties of the polymer indicate that it posseses an extended intermacrocycle π-conjugation. This results in a strong red shift of the macrocycle-derived Q-band with the polymer peak at 874 nm (1.42 eV) in solution and 838 nm (1.48 eV) in solid films compared with a monomer solution peak at 642 nm (1.93 eV). The polymer possesses a large Stark-shift-related DC Kerr electro-optic non-linearity with peak responses in the real and imaginary part of X(3) (−ω; 0, 0, ω) of ReX(3) = −7.2 × 10 −8 esu at 849 nm (1.46 eV) and lmX(3) = 6.7 × 10−8 esu at 855 nm (1.45 eV). This response is 3–10 tiems larger that that reported for quasi-one-dimesional conjugated polymers and enhancements can be anticipated. Detailed examination of the electro-optic response spectra shows several interesting features which indicated that the usual phenomenological models of molecular Stark shifts do not provide a full description of the abserved behaviour. Future studies are planned to look more closely at the nature of the electro-optic response.