(Invited) Advances in Silicon Nanophotonics

Silicon nanophotonics is emerging as a new platform for the integration of photonic and electronic devices. Several examples of recent efforts on monolithic light sources based on silicon nanostructures will be presented and discussed. In particular it will be shown that silicon-on-insulator (SOI) is emerging as an interesting photonic material. The first  electrically pumped silicon-on-insulator nano light source, tunable around 1300-1600nm range and operating at room temperature will be presented. H-related optically active defects are properly introduced into silicon enhancing the electrically driven emission in a photonic crystal nanocavity device. A narrow (Δλ = 0.5 nm) emission line with  the highest spectral power density ever reported from any silicon emitter will indeed be presented. Alternatively Er ions are introduced into the nanocavity showing an enhanced emission at 1500 nm with potentials for a population inversion and laser action. Group-IV semiconductor nanowires (NWs) are also attracting interest among the scientific community as building blocks for a wide range of future nanoscaled devices. We show that metal-assisted chemical etching is a powerful technique to obtain nanometer-size high density and low-cost Si NWs with high and controllable aspect ratio. NWs obtained by this technique have exactly the same structure and doping properties of the substrate and present quantum confinement effects. We will show that luminescence is very efficient (in the order of the percent) and tunable with NWs size according to quantum confinement. Light emitting devices based on Si NWs have also been realised, showing the efficient electroluminescence emission at room temperature under low voltage excitation. The relevance and  the perspectives of the reported results opening the route towards novel applications of Si nanostructures in photonics will be discussed.