3RD-ORDER OPTICAL NONLINEARITY OF COLLOIDAL METAL NANOCLUSTERS FORMEDBY MEV ION-IMPLANTATION

We report the results of characterization of nonlinear refractive inde x of the composite material produced by MeV Ag ion implantation of LiN bO3 crystal (z-cut). The material after implantation exhibited a linea r optical obsroption spectrum with the surface plasmon peak near 430 n m attributed to the colloidal silver nanoclusters. Heat treatment of t he material at 500 degrees C caused a shift of the absorption peak to 550 nm. The nonlinear refractive index of the sample after heat treatm ent was measured in the region of the absorption peak with the Z-scan technique using a tunable picosecond laser source (4.5 ps pulse width) . The experimental data were compared against the reference sample mad e of MeV Cu implanted silica with the absorption peak in the same regi on. The nonlinear index of the Ag implanted LiNbO3 sample produced at five times less fluence is on average two times greater than that of t he reference. (C) 1998 Elsevier Science B.V. All rights reserved.