Abstract

Optical limiting devices are currently of interest for protecting sensors and eyes from high intensity laser light, as well as for thresholding elements in optical processing systems. The JPL and CREOL groups have previously demonstrated that metallophthalocyanine dye solutions exhibit nonlinear absorption and can be used in optical limiters for picosecond and nanosecond laser pulses.^1-3 These dyes are normally weakly absorbing but when subjected to a strong flash of light significant populations of excited singlet or triplet states are produced, whereupon the material becomes strongly absorbing. The triplet state, T₁, is formed by a typically slow process called intersystem crossing from the excited singlet state, S₁, subsequent to excitation. Time-resolved absorption measurements on phthalocyanines subsequent to flash excitation have shown that excited triplet-state absorption can be stronger than excited singlet-state absorption, in the relevant spectral region.¹

© 1992 Optical Society of America