OPTICAL LIMITING CHARACTERISTICS AND MECHANISM OF SILVER BROMIDE NANOSOLS

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