Third-order nonlinearity and optical limiting studies in phosphorus (V) porphyrins with charge transfer states

Enhancement in the third-order nonlinearity chi((3)), nonlinear absorption and optical limiting threshold with the introduction of charge transfer (CT) states are observed in a new class of azoarene phosphorus (V) porphyrus. Introduction of axial azoarene groups into the phosphorus porphyrin structure led to a rise in the measured <gamma> values. Faster intersystem crossing from CT states to triplet and excited state absorption from the triplet states contribute to the enhancement of nonlinear absorption thereby reducing the optical limiting threshold by a factor of 2. (C) 2002 Elsevier Science B.V. All rights reserved.