Nonlinear optical properties and optical limiting performances of pentaazadentate metal complexes in solution

The passive optical limiters are of significant for protecting sensors and human eyes from high intensity laser. The selection of materials is still one of the key for optical power limiters. The nonlinear optical properties of pentaazadentate metal complexes (PMC) were measured, the third-order optical nonlinear polarizabilities of 1.19 approx. 3.38×10^-13 esu were obtained, from which the molecular second order hyperpolarizabilities of 8.0×10^-32 approx. 2.83×10^-31 esu were calculated. The optical limiting performances for PMC have been studied at 532 nm for 8 ns and 35 ps pulses by using nonlinear absorption technique, in which the reverse saturable absorptions in the T₁ and S₁ states were responsible for the optical limitings. Experimental results demonstrated that the peripheral substituents and center metal ions influenced the third-order optical nonlinearities and the optical limiting performances of PMC.