Chapter 2 - Metal nanocluster composite glasses

Abstract

This chapter is concerned with metal nanocluster composites formed by transition metal clusters embedded in silicate glasses, in which cluster concentration is below percolation limit (dispersed clusters); in particular, the systems are in the condition of quasi-static regime, where cluster radius is much smaller than the wavelength of the light used to probe its response and–most of all–the light used in a MNCG-based optoelectronic device. Composite materials formed by transition metal clusters embedded in glass matrices exhibit peculiar optical properties. The development of the cluster-matter field assumed a strong impact owing to the experimentalavailability of selected cluster beams and time-of-flight mass spectrometry techniques. In general, the problem of the modelization of the cluster behavior has followed either atomistic (bottom-up) approaches, which exploits ab initio techniques of the quantum chemistry, or top-down approaches, describing the cluster as a mesoscopic piece of bulk to be treated in the solid-state or statistical physics framework. This work gives particular emphasis to the third-order nonlinear optical properties, because their technological implications as well as their peculiarity in MNCGs deserve this detailed treatment. One of the greatest challenges for optics is the development of computer systems based on all-optical photonic switching devices replacing electronic ones, that is, with short time and energy consumption per switch.