Studies of third-order optical nonlinearity and nonlinear absorption in tetra tolyl porphyrins using degenerate four wave mixing and Z-scan

We present our experimental results on the measurement of third-order optic al nonlinearity in the ns and ps domain, in several Tetra Tolyl Porphyrin m olecules (TTP), using degenerate four wave mixing (DFWM) and Z-Scan techniq ues. Our results indicate a very high value of nonlinearity for these molec ules in the ns domain and reasonably high values in the ps domain. They are found to exhibit a strong nonlinear absorption at both 532 nm and 600 nm. The high value of nonlinearity for ns pulses is attributed to higher excite d singlet and triplet states. Time-resolved studies indicate an ultra-fast temporal evolution of the nonlinearity in these molecules. (C) 2000 Elsevie r Science B.V. All rights reserved.