Abstract

Materials that exhibit nonlinear absorption are currently of interest for use in devices that protect sensors and eyes from energetic light pulses, as well as for other optical limiting or switching applications. Dyes, such as metallophthaiocyanines, that exhibit weak ground state absorption followed by strong excited state absorption at the same wavelength have the right type of nonlinear absorption response for use in optical limiting.^1,2 Previous work has suggested the importance of excited sing let-sing) et and triplet-triplet absorptions to the optical limiting response of phthalocyanines. It was postulated¹ the enhanced optical limiting could be achieved by increasing the yield of the strongly absorbing triplet state, through use of the heavy atom effect, for example. We have recently demonstrated,³ for a series of phthalocyanines containing Si Ge and Sn, that the heavier metal atoms indeed lead to an enhancement in nonlinear absorption for nanosecond laser pulses. We present here new results on phthalocyanines containing Pb as well as group 3A metals·. AI,Ga, and In. We show that a rate equation model including excited singlet and triplet state absorption provides a good description of the nonlinear absorption data, and yields values for the excited state absorption cross sections.

© 1993 Optical Society of America