Abstract

Previously a considerable enhancement of various nonlinear-optical processes was observed when the silver microparticles in colloidal solution aggregate into fractal clusters. So, the efficiency of degenerate four-wave mixing in aggregated silver colloid was shown to be ~10⁶ times that of non-aggregated colloid.¹ The nonlinear absorption² and refraction³ appeared to increase with aggregation by a factor of ≈550 and ≈400, correspondingly. The mentioned effects are connected with the local third-order nonlinear response of the medium, namely, described by the same component ${\chi }_{iiii}^{(3)}$ of the nonlinear susceptibility tensor.

© 1999 Optical Society of America