Optical limiting and upconverted luminescence in metalloporphyrin-doped sol-gels

In this paper, optical limiting and upconverted luminescence have been demonstrated in metalloporphyrin of ZnTPPS-doped aluminosilicate sol-gel hosts. The photo-upconverted radiative emission was observed and believed to result from the radiative recombination of the second excited singlet state. Intensity of the upconverted luminescence was found to be saturated as a function of excitation intensity. Optical limiting associated with reverse saturable absorption was observed. These effects are attributed to the higher excited state absorption. A method for determining absorption cross-section of excited states was developed by using dynamic calculation to fit the intensity dependence of upconverted intensity. The absorption cross sections of the excited singlet and triplet state were estimated. (C) 1998 Elsevier Science Ltd. All rights reserved.