The use of light to channel signals around electronic chips could solve several current problems in microelectronic evolution including: power dissipation, interconnect bottlenecks, input/output from/to optical communication channels, poor signal bandwidth, etc. It is unfortunate that silicon is not a good photonic material: it has a poor light-emission efficiency and exhibits a negligible electro-optical effect. Silicon photonics is a field having the objective of improving the physical properties of silicon; thus turning it into a photonic material and permitting the full convergence of electronics and photonics.Various research efforts, based upon the use of nano-sized silicon, are described in this book. The authors review the field and report the recent research results achieved in Trento.The work is divided into the chapters: 1. Introduction, 2. Silicon nanocrystal fundamentals, 3. Nanoprobe technique to characterize Silicon nanocrystals, 4. Silicon-based light-emitting diode, 5. Optical gain in silicon and the quest for a silicon laser, 6. Er coupled Si nanocrystal optical amplifiers, 7. Design of silicon-based optical components, 8. Si-based waveguides, 9. Silicon-based photonic crystals, 10. Silicon-based complex dielectric systems.This is, altogether, a unique summary of a pivotal issue in semiconductor research.