We describe the picosecond nonlinear optical response of a metal-dielectric composite made by implanting Cu ions in fused silica. The implanted Cu ions aggregate during implantation to form nanometer-diameter clusters in a dense, thin (~150 nm) layer just beneath the surface of the substrate. The third-order susceptibility X((3)) has an electronic component with a magnitude of the order of 10(-8) esu and is enhanced for laser wavelengths near the surface plasmon resonance of the copper colloids.
Cu clusters of nanometer dimensions were created by implantation of Cu ions into pure fused silica substrates at energies of 160 keV. The sizes and size distributions of the Cu clusters were measured by transmission electron microscopy, and were found to be determined by the ion-beam current during implantation. Optical-absorption spectra of these materials show the size-dependent surface plasmon resonance characteristic of noble-metal clusters. There are also significant size-dependent effects in both the nonlinear index of refraction and two-photon absorption coefficients. The distinctive variations in linear and nonlinear optical properties with Cu nanocluster sizes and size distributions affords potentially interesting possibilities for using these materials in nonlinear optical devices.
Ion implantation was used to form compound semiconductor nanocrystal precipitates of ZnS, CdS, and PbS in both glass and crystalline matrices. The precipitate microstructures and size distributions were investigated by cross-sectional transmission electron microscopy techniques. Several unusual features were observed, including strongly depth-dependent size variations of the ZnS precipitates and central void features in the CdS nanocrystals. The morphology and crystal structure of the nanocrystal precipitates could be controlled by selection of the host material. The size distribution and microstructural complexity were significantly reduced by implanting a low concentration of ions into a noncrystalline host, and by using multi-energy implants to give a flat concentration profile of the implanted elements.
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