RESUMO
We reveal the generation of a broadband (> 1.9 THz) bi-photon quantum frequency comb (QFC) in a silicon-on-insulator (SOI) Fabry-Pérot micro-cavity and the control of its spectral correlation properties. Correlated photon pairs are generated through three spontaneous four-wave mixing (SFWM) processes by using a co-polarized bi-chromatic coherent input with power P1 and P2 on adjacent resonances of the nonlinear cavity. Adjusting the spectral power ratio r = P1/(P1 + P2) allows control over the influence of each process leading to an enhancement of the overall photon pair generation rate (PGR) µ(r) by a maximal factor of µ(r = 0.5)/µ(r = 0) ≈ 1.5, compared to the overall PGR provided by a single-pump configuration with the same power budget. We demonstrate that the efficiency aND of the non-degenerate excitation SFWM process (NDP) doubles the efficiency a1 ≈ a2 of the degenerate excitation SFWM processes (DP), showing a good agreement with the provided model.
RESUMO
Molecular dynamic simulations were performed to study the morphology and binding energy of the most stable isomers of silver clusters with diameters of less than 2 nm. A 5-fold symmetry was found in most cases, and a novel morphology for the clusters of 39 and 116 silver atoms was identified. This morphology can be understood in terms of decahedral and icosahedral geometries, which are intercalated, as we explain in detail. These kind of structures have been observed for gold and now are predicted for small and intermediate silver nanoparticles.