RESONANT NONLINEAR-OPTICAL STUDIES ON PORPHYRIN DERIVATIVES

The nonlinear optical properties of three porphyrin derivatives (T3,4 BCEMPP, T4 CEMPP and TPP) doped in boric acid glass were probed using the Z-scan technique at different argon-ion laser wavelengths. The non linear transmission characteristics of T3,4 BCEMPP and T4 CEMPP exhibi t saturable absorption at 457.9 nm and 476.5 nm while these are domina ted by excited state absorption at 488.0 nm. However, in the case of T PP, the excited state absorption dominates the nonlinear characteristi cs except at 457.9 nm. The experimental observations are explained by using the four-level saturable absorber model. Saturation intensity, e xcited state absorption cross-section, light-induced changes in the ab sorption and the refractive index along with its sign were determined at these argon-ion laser wavelengths. Furthermore, optical limiting ch aracteristics of these samples were studied. The observed limiting act ion is consistent with the Z-scan studies.