Optical limiting behavior has been observed in nanosols comprising similar to 60 Angstrom particles of silver bromide. Switching times, tau, are consistently in the ns regime, and values of I 1/2, the pulse laser exposure which elicits a 50% decrease in transmittance of the medium, can be less than 20 mJ/cm(2) Nonlinearity of response, I 1/2, and response time all increase with decreasing pAg [Eq. (2)] of the nanosols. The materials can be cycled apparently indefinitely, provided they are subjected only to very short (sub-ns) laser pulses. Optical switching can be spectrally sensitized; comparable response parameters are obtained under these conditions. The nonlinear character of the response is, however, very different: a true response threshold, I-0=similar to 12 mJ/cm(2), is observed. Analysis of the optical limiting mechanism suggests that iodide doping, which is adventitious in the present case, is critical to the observed photophysical behavior of the nanosols. (C) 1996 American Institute of Physics.
