Nonlinear absorption and refraction in porphyrazine derivatives Original Research Article

The nonlinear optic effects in the copper complexes of pyrazinoporphyrazines (AzaPhcCu 1a-b and 2a-b) is measured the first time with intensity-dependent transmittance and Z-scan methods at 532 nm and 8 ns pulse. We attribute the observed nonlinear absorption in these AzaPhcCu complexes to reverse saturable absorption mechanism which arises due to higher absorption from their excited states (especially the excitation process of S2(v)←S1(v=0)) than from the ground state. The observed sign and size of the nonlinear refractive indices in these AzaPhcCu solutions in CH2Cl2 (n2eff=2.66×10−10 esu in average) is comparable to that in CuPc, while the negative nonlinear refraction is due to the intramolecular relaxation between AzaPhcʹs triplet state and the heat released to the solution leading to another refractive index change.